RESEARCH LETTER
Fraser Syndrome Due to Mutations in GRIP1—Clinical Phenotype in Two Families and Expansion of the Mutation Spectrum Denny Schanze,1 Hu¨lya Kayserili,2 Bilge N. Satkın,2 Umut Altunoglu,2 and Martin Zenker1* 1
Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany
2
Istanbul Medical Faculty, Medical Genetics Department, Istanbul University, Istanbul, Turkey
Manuscript Received: 13 August 2013; Manuscript Accepted: 11 October 2013
TO THE EDITOR: Fraser syndrome (FS; OMIM 219000) is a genetically heterogeneous condition characterized by cryptophthalmos, syndactyly, and anomalies of the respiratory and urogenital tracts [Slavotinek and Tifft, 2002; van Haelst et al., 2007]. This congenital malformation syndrome is inherited as an autosomal recessive trait. Mutations in the genes FRAS1 (OMIM 607830) and, less frequently, FREM2 (OMIM 608945) are well-established causes of FS [McGregor et al., 2003; Jadeja et al., 2005], and together they account for the majority of cases [van Haelst et al., 2008]. FRAS1 and FRAS1related extracellular matrix (FREM) proteins form a mutually stabilized complex that is expressed in basement membranes during embryonic development and contributes to embryonic epithelial– mesenchymal integrity [Smyth and Scambler, 2005; Kiyozumi et al., 2006]. More recently, GRIP1 mutations were identified as another cause of Fraser syndrome in three families [Vogel et al., 2012]. GRIP1 (OMIM 604597) encodes a scaffolding protein that directly interacts with FRAS1/FREM protein complexes and is required for their localization to the basal side of cells. Grip1 mutations in mice are known to cause FS-like defects [Smyth and Scambler, 2005]. Herein we describe two additional families affected by Fraser syndrome due to GRIP1 mutations, thereby expanding the clinical and mutation spectrum. Patient 1, a female fetus, was the progeny from the ninth pregnancy of a consanguineous, double first cousin, Turkish couple. Pregnancy was terminated at 17 weeks of gestation due to antenatal ultrasound findings of bilateral renal agenesis complicated with anhydramnios. The stillborn fetus showed bilateral ablepharon, hypertelorism, structurally abnormal, low-set and posteriorly rotated ears, short nose with hypoplastic nares and a bifid nasal tip, cutaneous syndactyly of hands and feet, ambiguous genitalia with clitoromegaly, as well as hypoplasia of labia majora and minora (Fig. 1A). The couple had a healthy daughter and six spontaneous abortions between the 6th and 16th weeks of gestation with unknown etiology. In one additional pregnancy complicated with oligohydramnios, the stillborn fetus at 22 gestational weeks showed bilateral hydronephrosis, occipital encephalocele, and bilateral polydactyly of hands, which was considered as suggestive for Meckel– Gruber syndrome but could also be compatible with Fraser syndrome. No material for genetic testing was available from this fetus.
Ó 2013 Wiley Periodicals, Inc.
How to Cite this Article: Schanze D, Kayserili H, Satkın BN, Altunoglu U, Zenker M. 2014. Fraser syndrome due to mutations in GRIP1— Clinical phenotype in two families and expansion of the mutation spectrum. Am J Med Genet Part A 164A:837–840.
Patient 2 was born from the fifth pregnancy of a healthy unrelated Turkish couple. The girl was referred to the genetics outpatient clinics at the age of 2.5 months for further evaluation of multiple congenital anomalies. She had bilateral palpebral defects with micro-symblepharon on the left and upper eyelid coloboma on the right, cutaneous syndactyly of both hands (partial on the right and almost complete on the left), and clitoral hypertrophy with absence of labia minora (Fig. 1B). Renal ultrasound revealed right-sided renal agenesis and left-sided grade II hydronephrosis. She had been operated for a laryngeal web as a newborn, and after reconstructive surgery for syndactyly at the age of one, she had to have tracheostomy in the early postoperative period. She had multiple additional surgeries to correct left hand syndactyly and the eyelid defects. Despite these measures and treatment with lubricating eye drops she developed keratitis, corneal clouding and a fibrovascular pannus on the left eye with loss of vision, as well as a limbal pterygium on the right. She Conflict of interest: none. Schanze and Kayserili contributed equally to this work. Grant sponsor: Scientific and Technological Research Council of Turkey ¨ BI˙TAK); Grant number: 112S398; Grant sponsor: European (TU Research Area Network (E-RARE, project); Grant number: CRANIRARE-2. Correspondence to: Prof. Dr. Med. Martin Zenker, Institute of Human Genetics, University Hospital Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany. E-mail: [email protected] Article first published online in Wiley Online Library (wileyonlinelibrary.com): 19 December 2013 DOI 10.1002/ajmg.a.36343
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FIG. 1. Clinical and molecular findings in two families with GRIP1 mutations. A: Patient 1 as a 17 weeks old female fetus showing typical facial anomalies of FS, ambiguous genitalia, and cutaneous syndactyly of fingers and toes. B: Patient 2 at age 2.5 months and 3 years, respectively, showing typical facial anomalies of FS, ambiguous genitalia, and cutaneous syndactyly of both hands. C: Chromatograms showing part of GRIP1 exon 16 in a control, the homozygous mutation c.1860C>A in Patient 1, and the heterozygous state in the mother and father. The mutation is indicated by ( ). D: Chromatograms showing part of GRIP1 exon 18 with the hemizygous mutation c.2120C>A in Patient 2 and the heterozygous state in the father. Only the wild type allele is observed in the mother as in the control. The mutation is indicated by ( ). An additional homozygous SNP inherited by the father and not present in the mother is indicated by (˚). E: Array CGH results of the mother showing a deletion of approximately 2 kb encompassing exons 17 and 18 of GRIP1 gene, each represented by four probes.
developed middle ear effusion resulting in transient conductive type hearing loss, which resolved after surgery. At the last visit at the age of 3 years, her height, weight, and head circumference were within the normal ranges. Aside from the anomalies mentioned above, dysmor-
phological evaluation also noted abnormal frontal hair extending from the left temporal region to the lateral eye margin, short structurally abnormal ears, broad and low nasal bridge with underdeveloped and mildly notched alae nasi, long columella, smooth philtrum, and widely
SCHANZE ET AL. spaced nipples (Fig. 1B). Developmental assessment by the DENVER II test showed that her gross motor skills were appropriate for age, while fine motor, social, and language skills were mildly delayed by 6 months, which could be at least in part attributed to her hand malformations and hearing problems. The parents previously had two spontaneous abortions and two medical abortions due to severe oligohydramnios possibly secondary to renal agenesis. No autopsy results are available from the latter, but fixed, paraffin embedded tissue samples were stored from each fetus, which could be used for DNA extraction. Index patients of both families had been tested negative for mutations in FRAS1 and FREM2, previously. All coding exons including exon–intron boundaries of GRIP1 were analyzed by bidirectional direct sequencing using the BigDyeTerminator kit v3.1 (Life Technologies, Darmstadt, Germany) and an automated capillary sequencer (3500xl Genetic Analyzer, Life Technologies). Oligonucleotide primer sequences and PCR conditions are available upon request. Obtained sequences were compared with the reference sequence available in the public database (NM_021150.3). In Patient 1, a homozygous nonsense mutation c.1860C>A, p. (Tyr620 ) in exon 16 of GRIP1 gene was found. Further testing confirmed the heterozygous carrier status of the parents (Fig. 1C). In Patient 2, an apparently homozygous nonsense mutation c.2120C>A, p.(Ser707 ) in exon 18 of GRIP1 was detected. Both parents were tested but only the carrier status of the father for this variant was confirmed (Fig. 1D). Genotyping of additional intragenic SNPs indicated that the mutation was hemizygous in the index patient, while the maternally inherited allele harbored a deletion encompassing at least exon 18 but sparing the 50 part of the GRIP1 gene, exons 1–12 (data not shown). High-resolution array-CGH using an NimbleGen 630K CGH array (Roche NimbleGen, Inc., Madison, WI) revealed that the deletion breakpoints are probably located within introns 16 and 18 (Fig. 1E). The deletion of exons 17 and 18 predicts a shift of the reading frame and is therefore very likely the pathogenic disease-causing variant. The same genotype revealed in the index was also confirmed in the DNA from tissue samples of the two fetuses aborted due to oligohydramnios, thus confirming that they were affected by Fraser syndrome. The findings reported herein expand the GRIP1 mutation spectrum, which includes nonsense, frameshift, and splice site mutations, as well as one larger genomic deletion. This is a typical mutational spectrum for recessive disorders that are caused by a complete or near-complete loss of the gene product. Clinically, the patients presented here together with the previously published ones illustrate that GRIP1 mutations are associated with a phenotype that is indistinguishable from FS caused by FRAS1 or FREM2 mutations. All the well-known major features of FS are also common in patients with GRIP1 mutations, namely the cryptophthalmos spectrum (5/5), uni- or bilateral renal agenesis (5/5), cutaneous syndactyly (3/4), abnormal genitalia (4/4), broad or bifid nose with or without notched nares (5/5), and small and/or dysplastic ears (4/4). Other less frequent but distinctive features of FS were likewise observed among GRIP1-mutated patients, such as laryngeal atresia/stenosis, abnormal lung lobulation, misplaced and stenotic anus, and low insertion of the umbilicus [Vogel et al., 2012 and patients presented here]. The lack of obvious genotype phenotype correlations is in line with the findings that FRAS1, FREM2,
839 and GRIP1 are essential components of the same protein complex, and the absence of either of these components leads to lack of expression of the other components at the embryonic basement membranes, as well [Kiyozumi et al., 2006]. However, GRIP1 protein is also known to make other important molecular interactions besides its participation in the FRAS1/FREM complex, particularly in the central nervous system [Setou et al., 2002; Liu and Cull-Candy, 2005]. The neurodevelopmental status of Patient 2 reported here does not provide evidence of a major defect in brain development or function. Nevertheless, the number of observed cases with GRIP1 mutations is far too small to rule out more subtle genotype phenotype correlations. Among approximately 50 unrelated FS patients who had molecular genetic confirmation at our laboratory, so far, GRIP1 mutations were found in only three families, thus accounting for less than 10% of the entire cohort (unpublished data, M. Zenker). The small number of FS patients diagnosed with GRIP1 mutations may simply be related to a lower GRIP1 mutation carrier frequency in the general population. However, it might also be caused by a high antenatal lethality of affected fetuses. In this context it is noteworthy that Patient 2 described here is the only living patient among those reported with GRIP1 mutations, although it has to be admitted that this proportion is partly artificial since three of five reported index cases were medical abortions [Vogel et al., 2012 and present report]. In each of the two families reported here, there were multiple abortions. Fetal FS could retrospectively be confirmed in two pregnancies terminated due to oligohydramnios in Family 2, but there might have been additional FS patients among the spontaneous abortuses in either of these families. Current experience is still insufficient to postulate a positive correlation between GRIP1 mutations and early lethality, thus underscoring the need for reporting further observations. There is little knowledge about the frequency of intrauterine deaths due to FS, in general, but spontaneous fetal loss has repeatedly been observed, and among induced abortions for bilateral renal agenesis there is probably another undiagnosed fraction of fetuses with FS. As a consequence, FS has to be considered in the differential diagnosis of any fetus with renal agenesis, and GRIP1 has to be included in the list of genes to be tested in patients with a clinical suspicion of FS—not least in antenatal lethal cases.
ACKNOWLEDGMENTS We thank the families for their participation in our research project and Ilka Kramer for excellent technical assistance. This project was partially supported by the grant 112S398 from the Scientific and ¨ BI˙TAK) for the Technological Research Council of Turkey (TU consortium CRANIRARE-2 supported by the European Research Area Network (E-RARE, project) to H.K.
REFERENCES Jadeja S, Smyth I, Pitera JE, Taylor MS, van Haelst M, Bentley E, McGregor L, Hopkins J, Chalepakis G, Philip N, Perez Aytes A, Watt FM, Darling SM, Jackson I, Woolf AS, Scambler PJ. 2005. Identification of a new gene mutated in Fraser syndrome and mouse myelencephalic blebs. Nat Genet 37:520–525.
840 Kiyozumi D, Sugimoto N, Sekiguchi K. 2006. Breakdown of the reciprocal stabilization of QBRICK/Frem1, Fras1, and Frem2 at the basement membrane provokes Fraser syndrome-like defects. Proc Natl Acad Sci USA 103:11981–11986. Liu SJ, Cull-Candy SG. 2005. Subunit interaction with PICK and GRIP controls Ca2þ permeability of AMPARs at cerebellar synapses. Nat Neurosci 8:768–775. McGregor L, Makela V, Darling SM, Vrontou S, Chalepakis G, Roberts C, Smart N, Rutland P, Prescott N, Hopkins J, Bentley E, Shaw A, Roberts E, Mueller R, Jadeja S, Philip N, Nelson J, Francannet C, Perez-Aytes A, Megarbane A, Kerr B, Wainwright B, Woolf AS, Winter RM, Scambler PJ. 2003. Fraser syndrome and mouse blebbed phenotype caused by mutations in FRAS1/Fras1 encoding a putative extracellular matrix protein. Nat Genet 34:203–208. Setou M, Seog DH, Tanaka Y, Kanai Y, Takei Y, Kawagishi M, Hirokawa N. 2002. Glutamate-receptor-interacting protein GRIP1 directly steers kinesin to dendrites. Nature 417:83–87.
AMERICAN JOURNAL OF MEDICAL GENETICS PART A Slavotinek AM, Tifft CJ. 2002. Fraser syndrome and cryptophthalmos: Review of the diagnostic criteria and evidence for phenotypic modules in complex malformation syndromes. J Med Genet 39:623–633. Smyth I, Scambler P. 2005. The genetics of Fraser syndrome and the blebs mouse mutants. Hum Mol Genet 14:R269–R274. van Haelst MM, Scambler PJ, Fraser Syndrome Collaboration G, Hennekam RC. 2007. Fraser syndrome: A clinical study of 59 cases and evaluation of diagnostic criteria. Am J Med Genet Part A 143A:3194–3203. van Haelst MM, Maiburg M, Baujat G, Jadeja S, Monti E, Bland E, Pearce K, Fraser Syndrome Collaboration G, Hennekam RC, Scambler PJ. 2008. Molecular study of 33 families with Fraser syndrome new data and mutation review. Am J Med Genet Part A 146A:2252–2257. Vogel MJ, van Zon P, Brueton L, Gijzen M, van Tuil MC, Cox P, Schanze D, Kariminejad A, Ghaderi-Sohi S, Blair E, Zenker M, Scambler PJ, Ploos van Amstel HK, van Haelst MM. 2012. Mutations in GRIP1 cause Fraser syndrome. J Med Genet 49:303–306.
Fraser Syndrome Due to Mutations in GRIP1—Clinical Phenotype in Two Families and Expansion of the Mutation Spectrum Denny Schanze,1 Hu¨lya Kayserili,2 Bilge N. Satkın,2 Umut Altunoglu,2 and Martin Zenker1* 1
Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany
2
Istanbul Medical Faculty, Medical Genetics Department, Istanbul University, Istanbul, Turkey
Manuscript Received: 13 August 2013; Manuscript Accepted: 11 October 2013
TO THE EDITOR: Fraser syndrome (FS; OMIM 219000) is a genetically heterogeneous condition characterized by cryptophthalmos, syndactyly, and anomalies of the respiratory and urogenital tracts [Slavotinek and Tifft, 2002; van Haelst et al., 2007]. This congenital malformation syndrome is inherited as an autosomal recessive trait. Mutations in the genes FRAS1 (OMIM 607830) and, less frequently, FREM2 (OMIM 608945) are well-established causes of FS [McGregor et al., 2003; Jadeja et al., 2005], and together they account for the majority of cases [van Haelst et al., 2008]. FRAS1 and FRAS1related extracellular matrix (FREM) proteins form a mutually stabilized complex that is expressed in basement membranes during embryonic development and contributes to embryonic epithelial– mesenchymal integrity [Smyth and Scambler, 2005; Kiyozumi et al., 2006]. More recently, GRIP1 mutations were identified as another cause of Fraser syndrome in three families [Vogel et al., 2012]. GRIP1 (OMIM 604597) encodes a scaffolding protein that directly interacts with FRAS1/FREM protein complexes and is required for their localization to the basal side of cells. Grip1 mutations in mice are known to cause FS-like defects [Smyth and Scambler, 2005]. Herein we describe two additional families affected by Fraser syndrome due to GRIP1 mutations, thereby expanding the clinical and mutation spectrum. Patient 1, a female fetus, was the progeny from the ninth pregnancy of a consanguineous, double first cousin, Turkish couple. Pregnancy was terminated at 17 weeks of gestation due to antenatal ultrasound findings of bilateral renal agenesis complicated with anhydramnios. The stillborn fetus showed bilateral ablepharon, hypertelorism, structurally abnormal, low-set and posteriorly rotated ears, short nose with hypoplastic nares and a bifid nasal tip, cutaneous syndactyly of hands and feet, ambiguous genitalia with clitoromegaly, as well as hypoplasia of labia majora and minora (Fig. 1A). The couple had a healthy daughter and six spontaneous abortions between the 6th and 16th weeks of gestation with unknown etiology. In one additional pregnancy complicated with oligohydramnios, the stillborn fetus at 22 gestational weeks showed bilateral hydronephrosis, occipital encephalocele, and bilateral polydactyly of hands, which was considered as suggestive for Meckel– Gruber syndrome but could also be compatible with Fraser syndrome. No material for genetic testing was available from this fetus.
Ó 2013 Wiley Periodicals, Inc.
How to Cite this Article: Schanze D, Kayserili H, Satkın BN, Altunoglu U, Zenker M. 2014. Fraser syndrome due to mutations in GRIP1— Clinical phenotype in two families and expansion of the mutation spectrum. Am J Med Genet Part A 164A:837–840.
Patient 2 was born from the fifth pregnancy of a healthy unrelated Turkish couple. The girl was referred to the genetics outpatient clinics at the age of 2.5 months for further evaluation of multiple congenital anomalies. She had bilateral palpebral defects with micro-symblepharon on the left and upper eyelid coloboma on the right, cutaneous syndactyly of both hands (partial on the right and almost complete on the left), and clitoral hypertrophy with absence of labia minora (Fig. 1B). Renal ultrasound revealed right-sided renal agenesis and left-sided grade II hydronephrosis. She had been operated for a laryngeal web as a newborn, and after reconstructive surgery for syndactyly at the age of one, she had to have tracheostomy in the early postoperative period. She had multiple additional surgeries to correct left hand syndactyly and the eyelid defects. Despite these measures and treatment with lubricating eye drops she developed keratitis, corneal clouding and a fibrovascular pannus on the left eye with loss of vision, as well as a limbal pterygium on the right. She Conflict of interest: none. Schanze and Kayserili contributed equally to this work. Grant sponsor: Scientific and Technological Research Council of Turkey ¨ BI˙TAK); Grant number: 112S398; Grant sponsor: European (TU Research Area Network (E-RARE, project); Grant number: CRANIRARE-2. Correspondence to: Prof. Dr. Med. Martin Zenker, Institute of Human Genetics, University Hospital Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany. E-mail: [email protected] Article first published online in Wiley Online Library (wileyonlinelibrary.com): 19 December 2013 DOI 10.1002/ajmg.a.36343
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FIG. 1. Clinical and molecular findings in two families with GRIP1 mutations. A: Patient 1 as a 17 weeks old female fetus showing typical facial anomalies of FS, ambiguous genitalia, and cutaneous syndactyly of fingers and toes. B: Patient 2 at age 2.5 months and 3 years, respectively, showing typical facial anomalies of FS, ambiguous genitalia, and cutaneous syndactyly of both hands. C: Chromatograms showing part of GRIP1 exon 16 in a control, the homozygous mutation c.1860C>A in Patient 1, and the heterozygous state in the mother and father. The mutation is indicated by ( ). D: Chromatograms showing part of GRIP1 exon 18 with the hemizygous mutation c.2120C>A in Patient 2 and the heterozygous state in the father. Only the wild type allele is observed in the mother as in the control. The mutation is indicated by ( ). An additional homozygous SNP inherited by the father and not present in the mother is indicated by (˚). E: Array CGH results of the mother showing a deletion of approximately 2 kb encompassing exons 17 and 18 of GRIP1 gene, each represented by four probes.
developed middle ear effusion resulting in transient conductive type hearing loss, which resolved after surgery. At the last visit at the age of 3 years, her height, weight, and head circumference were within the normal ranges. Aside from the anomalies mentioned above, dysmor-
phological evaluation also noted abnormal frontal hair extending from the left temporal region to the lateral eye margin, short structurally abnormal ears, broad and low nasal bridge with underdeveloped and mildly notched alae nasi, long columella, smooth philtrum, and widely
SCHANZE ET AL. spaced nipples (Fig. 1B). Developmental assessment by the DENVER II test showed that her gross motor skills were appropriate for age, while fine motor, social, and language skills were mildly delayed by 6 months, which could be at least in part attributed to her hand malformations and hearing problems. The parents previously had two spontaneous abortions and two medical abortions due to severe oligohydramnios possibly secondary to renal agenesis. No autopsy results are available from the latter, but fixed, paraffin embedded tissue samples were stored from each fetus, which could be used for DNA extraction. Index patients of both families had been tested negative for mutations in FRAS1 and FREM2, previously. All coding exons including exon–intron boundaries of GRIP1 were analyzed by bidirectional direct sequencing using the BigDyeTerminator kit v3.1 (Life Technologies, Darmstadt, Germany) and an automated capillary sequencer (3500xl Genetic Analyzer, Life Technologies). Oligonucleotide primer sequences and PCR conditions are available upon request. Obtained sequences were compared with the reference sequence available in the public database (NM_021150.3). In Patient 1, a homozygous nonsense mutation c.1860C>A, p. (Tyr620 ) in exon 16 of GRIP1 gene was found. Further testing confirmed the heterozygous carrier status of the parents (Fig. 1C). In Patient 2, an apparently homozygous nonsense mutation c.2120C>A, p.(Ser707 ) in exon 18 of GRIP1 was detected. Both parents were tested but only the carrier status of the father for this variant was confirmed (Fig. 1D). Genotyping of additional intragenic SNPs indicated that the mutation was hemizygous in the index patient, while the maternally inherited allele harbored a deletion encompassing at least exon 18 but sparing the 50 part of the GRIP1 gene, exons 1–12 (data not shown). High-resolution array-CGH using an NimbleGen 630K CGH array (Roche NimbleGen, Inc., Madison, WI) revealed that the deletion breakpoints are probably located within introns 16 and 18 (Fig. 1E). The deletion of exons 17 and 18 predicts a shift of the reading frame and is therefore very likely the pathogenic disease-causing variant. The same genotype revealed in the index was also confirmed in the DNA from tissue samples of the two fetuses aborted due to oligohydramnios, thus confirming that they were affected by Fraser syndrome. The findings reported herein expand the GRIP1 mutation spectrum, which includes nonsense, frameshift, and splice site mutations, as well as one larger genomic deletion. This is a typical mutational spectrum for recessive disorders that are caused by a complete or near-complete loss of the gene product. Clinically, the patients presented here together with the previously published ones illustrate that GRIP1 mutations are associated with a phenotype that is indistinguishable from FS caused by FRAS1 or FREM2 mutations. All the well-known major features of FS are also common in patients with GRIP1 mutations, namely the cryptophthalmos spectrum (5/5), uni- or bilateral renal agenesis (5/5), cutaneous syndactyly (3/4), abnormal genitalia (4/4), broad or bifid nose with or without notched nares (5/5), and small and/or dysplastic ears (4/4). Other less frequent but distinctive features of FS were likewise observed among GRIP1-mutated patients, such as laryngeal atresia/stenosis, abnormal lung lobulation, misplaced and stenotic anus, and low insertion of the umbilicus [Vogel et al., 2012 and patients presented here]. The lack of obvious genotype phenotype correlations is in line with the findings that FRAS1, FREM2,
839 and GRIP1 are essential components of the same protein complex, and the absence of either of these components leads to lack of expression of the other components at the embryonic basement membranes, as well [Kiyozumi et al., 2006]. However, GRIP1 protein is also known to make other important molecular interactions besides its participation in the FRAS1/FREM complex, particularly in the central nervous system [Setou et al., 2002; Liu and Cull-Candy, 2005]. The neurodevelopmental status of Patient 2 reported here does not provide evidence of a major defect in brain development or function. Nevertheless, the number of observed cases with GRIP1 mutations is far too small to rule out more subtle genotype phenotype correlations. Among approximately 50 unrelated FS patients who had molecular genetic confirmation at our laboratory, so far, GRIP1 mutations were found in only three families, thus accounting for less than 10% of the entire cohort (unpublished data, M. Zenker). The small number of FS patients diagnosed with GRIP1 mutations may simply be related to a lower GRIP1 mutation carrier frequency in the general population. However, it might also be caused by a high antenatal lethality of affected fetuses. In this context it is noteworthy that Patient 2 described here is the only living patient among those reported with GRIP1 mutations, although it has to be admitted that this proportion is partly artificial since three of five reported index cases were medical abortions [Vogel et al., 2012 and present report]. In each of the two families reported here, there were multiple abortions. Fetal FS could retrospectively be confirmed in two pregnancies terminated due to oligohydramnios in Family 2, but there might have been additional FS patients among the spontaneous abortuses in either of these families. Current experience is still insufficient to postulate a positive correlation between GRIP1 mutations and early lethality, thus underscoring the need for reporting further observations. There is little knowledge about the frequency of intrauterine deaths due to FS, in general, but spontaneous fetal loss has repeatedly been observed, and among induced abortions for bilateral renal agenesis there is probably another undiagnosed fraction of fetuses with FS. As a consequence, FS has to be considered in the differential diagnosis of any fetus with renal agenesis, and GRIP1 has to be included in the list of genes to be tested in patients with a clinical suspicion of FS—not least in antenatal lethal cases.
ACKNOWLEDGMENTS We thank the families for their participation in our research project and Ilka Kramer for excellent technical assistance. This project was partially supported by the grant 112S398 from the Scientific and ¨ BI˙TAK) for the Technological Research Council of Turkey (TU consortium CRANIRARE-2 supported by the European Research Area Network (E-RARE, project) to H.K.
REFERENCES Jadeja S, Smyth I, Pitera JE, Taylor MS, van Haelst M, Bentley E, McGregor L, Hopkins J, Chalepakis G, Philip N, Perez Aytes A, Watt FM, Darling SM, Jackson I, Woolf AS, Scambler PJ. 2005. Identification of a new gene mutated in Fraser syndrome and mouse myelencephalic blebs. Nat Genet 37:520–525.
840 Kiyozumi D, Sugimoto N, Sekiguchi K. 2006. Breakdown of the reciprocal stabilization of QBRICK/Frem1, Fras1, and Frem2 at the basement membrane provokes Fraser syndrome-like defects. Proc Natl Acad Sci USA 103:11981–11986. Liu SJ, Cull-Candy SG. 2005. Subunit interaction with PICK and GRIP controls Ca2þ permeability of AMPARs at cerebellar synapses. Nat Neurosci 8:768–775. McGregor L, Makela V, Darling SM, Vrontou S, Chalepakis G, Roberts C, Smart N, Rutland P, Prescott N, Hopkins J, Bentley E, Shaw A, Roberts E, Mueller R, Jadeja S, Philip N, Nelson J, Francannet C, Perez-Aytes A, Megarbane A, Kerr B, Wainwright B, Woolf AS, Winter RM, Scambler PJ. 2003. Fraser syndrome and mouse blebbed phenotype caused by mutations in FRAS1/Fras1 encoding a putative extracellular matrix protein. Nat Genet 34:203–208. Setou M, Seog DH, Tanaka Y, Kanai Y, Takei Y, Kawagishi M, Hirokawa N. 2002. Glutamate-receptor-interacting protein GRIP1 directly steers kinesin to dendrites. Nature 417:83–87.
AMERICAN JOURNAL OF MEDICAL GENETICS PART A Slavotinek AM, Tifft CJ. 2002. Fraser syndrome and cryptophthalmos: Review of the diagnostic criteria and evidence for phenotypic modules in complex malformation syndromes. J Med Genet 39:623–633. Smyth I, Scambler P. 2005. The genetics of Fraser syndrome and the blebs mouse mutants. Hum Mol Genet 14:R269–R274. van Haelst MM, Scambler PJ, Fraser Syndrome Collaboration G, Hennekam RC. 2007. Fraser syndrome: A clinical study of 59 cases and evaluation of diagnostic criteria. Am J Med Genet Part A 143A:3194–3203. van Haelst MM, Maiburg M, Baujat G, Jadeja S, Monti E, Bland E, Pearce K, Fraser Syndrome Collaboration G, Hennekam RC, Scambler PJ. 2008. Molecular study of 33 families with Fraser syndrome new data and mutation review. Am J Med Genet Part A 146A:2252–2257. Vogel MJ, van Zon P, Brueton L, Gijzen M, van Tuil MC, Cox P, Schanze D, Kariminejad A, Ghaderi-Sohi S, Blair E, Zenker M, Scambler PJ, Ploos van Amstel HK, van Haelst MM. 2012. Mutations in GRIP1 cause Fraser syndrome. J Med Genet 49:303–306.
