Clin Genet 2015: 87: 496–498 Printed in Singapore. All rights reserved
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd CLINICAL GENETICS doi: 10.1111/cge.12466
Letter to the Editor
Autosomal recessive mutations in the COL2A1 gene cause severe spondyloepiphyseal dysplasia To the Editor, Spondyloepiphyseal dysplasia congenita (SEDC, MIM 183900) is a skeletal dysplasia caused by heterozygous mutations in COL2A1, the gene encoding α1-chains of type II collagen (1). Affected individuals are disproportionately short with spinal deformities, cleft palate, myopia and hearing impairment. Skeletal surveys show platyspondyly, retarded ossification of pubic bones, epiphyseal and occasionally metaphyseal abnormalities (1). Here we report on a patient with severe SEDC and homozygosity for a novel COL2A1 mutation: p.Arg437Trp. The proband is the first child of second cousins from India with no familial history of skeletal dysplasia. He
was operated for pyloric stenosis at 1 month, and for inguinal hernia at 4 years. At 2 years of age, motor delay and short stature were noticed. Skeletal survey indicated SEDC with more severe epiphyseal dysplasia of the knees and ankles and bulbous ends of the phalanges (Fig. 1a–f). At 12 years he had severe short stature and kyphoscoliosis, a barrel-shaped chest, short neck, flat face, waddling gait, brachydactyly and myopia (−6.5/−7.5 D) with normal hearing. Auxological data are summarized in Table 1. Owing to genua valga, two corrective osteotomies were performed. The patient was on metformin treatment because of insulin resistance. The mother (36 years), father (39 years) and brother (7 years) were of average stature, had normal sight and hearing,
Fig. 1. Characteristic radiographic findings consistent with a diagnosis of severe spondyloepiphyseal dysplasia congenita (SEDC) and confirmation of the COL2A1 mutation c.1309C>T; p.Arg437Trp by Sanger sequencing. (a) Severe generalized platyspondyly with defective ossification of anterior parts of vertebral bodies in the spine (11 years). (b, c) Note that the epiphyseal dysplasia of the knee and ankle is more severe in this patient than typically seen in SEDC. Mild metaphyseal dysplasia of the lower femur and upper tibia (5 years and 3 months). (d) Short humerus with very broad bulbous metaphysis and small epiphysis (5 years and 3 months). (e) Short bulbous metacarpal bones, bulbous ends of the phalanges, and pseudoepiphysis of the second metacarpal bone. Slight shortening of the radius relative to ulna (5 years and 3 months). (f) Absence of ossification of femoral heads. Severe shortness of femoral neck. Hypoplasia of basilary portions of os ilium and of os pubis (5 years and 3 months). (g) Homozygous c.1309C>T mutation in the patient (a′ ) and heterozygous in his unaffected family members (b′ –d′ ). indicated by arrows c.1309C>T; p.Arg437Trp by Sanger sequencing.
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Letter to the Editor Table 1. Auxology data of the patient. Midparental height (MPH) 169.15 cm (Z score −1.81). The patient had a birth weight of 3150 g and birth length of 49 cm. Height of the patient at 11 years 9 month of age was 117.5 cm Z-score Age (years) Birth 0.25 1 4 5 8 9 10 11
Difference (cm)
Z-score for difference in:
Length/height*
Weight*
Relative sitting height†
Arm span – height
Length/height – MPH
−0.78 −1.09 −2.73 −2.97 −2.67 −4.37 −4.78 −5.12 −5.56
−0.88 −1.43 −2.27 +0.42 +2.13 +3.00 +2.81 +1.94 +0.95
NA NA NA NA NA NA +5.00 +6.87 +6.70
NA NA NA NA NA NA +1.4 +2.0 +1.1
+1.03 +0.72 −0.92 −1.16 −0.86 −2.56 −2.97 −3.31 −3.75
NA, not available. *Z-score for weight and height at birth and at follow up are based on Swedish standards from Albertsson Wikland K, Luo Z, Niklassson A et al. Swedish population-based longitudinal reference values from birth to 18 years of age for height, weight and head circumference. Acta Pediatrica 2002: 91: 739–754. †Z-scores for relative sitting height are calculated according to Dutch standards from Fredriks A, van Buuren S, van Heel W et al. Nationwide references for sitting height, leg length and sitting height/height ratio and their diagnostic value for disproportionate growth disorders. Archives Disease Childhood 2005: 90 (Suppl. 1): 55–65.
no joint pain or palatal abnormalities. The father suffers from multiple mandibular and patellar luxations. Skeletal surveys of both parents were normal. The patient was homozygous for a novel variant in COL2A1: NM_001844 c.1309C > T (exon 21), p.Arg437Trp. The variant was predicted to be damaging by SIFT, Align GVGD, and PolyPhen2 and alters a highly conserved nucleotide and amino acid, replacing a positively charged polar arginine with an aromatic and hydrophobic tryptophan. c.1309C>T has not been reported in healthy individuals in 135 local exomes, the 1000 genomes browser, ClinVar, dbSNP v137, or ESP6500. Extended testing was performed with: whole exome sequencing using TruSeq (Illumina, San Diego, CA) with 94–96% ×10 coverage; comparative genome hybridization array (array-CGH with a resolution of 50 kb) (Agilent Technologies, Paulo Alto, CA); and a high resolution targeted array-CGH for 226 known skeletal dysplasia genes, including COL2A1. No other disease causing genetic abnormalities were revealed. The parents and the brother were heterozygous for the COL2A1 mutation (Fig. 1g). Heterozygous mutations in COL2A1 give rise to a wide range of disorders including SEDC and there is limited genotype–phenotype correlation (1). Most mutations in COL2A1 involve the triple helix domain. The majority affect a glycine required for correct conformation of the triple helix and exert a dominant negative effect, leading to severe phenotypes (achondrogenesis, hypochondrogenesis and SEDC) (1). Arginine to cysteine substitutions are generally milder causing spondyloarthropathy and Stickler syndrome, but rarely SEDC (2). Non-glycine, non-cysteine missense mutations in the COL2A1 gene constitute only 2% of reported missense mutations and are associated with milder phenotypes (https://grenada.lumc.nl/LOVD2/ mendelian_genes/home.php?select_db=COL2A1). We
hypothesize that the p.Arg437Trp is even milder, with no clinically evident effect in the heterozygous state. Mouse homozygous for col2a1 mutations usually succumb perinatally (3). However, mice homozygous for p.Arg1417Cys mutation in col2a1 are viable with skeletal dysplasia, retinal abnormalities and hearing loss (4). This mouse model shows that specific homozygous mutations in COL2A1 are compatible with life. This is further supported by the recent conference report on five patients with possible autosomal recessive COL2A1 mutations (5). Additionally, autosomal recessive mutations have been reported in collagens IX and XI that covalently interact with collagen II (6, 7). In conclusion, our finding of biallelic mutations in the COL2A1 gene as a cause for severe SEDC is in line with observations in other collagenopathies, and extends the genetic and phenotypic spectrum of COL2A1-related disorders. Acknowledgements We are grateful to the patient and his family for participation and associated professor Lars Hagenäs for discussions. Financial support was provided through the regional agreement on medical training and clinical research (ALF) between Stockholm County Council and Karolinska Institutet, the Swedish Research Council, and, in addition, by grants from Kronprinsessan Lovisas and Axel Tiellmans Minnesfond, Frimurare Barnhuset i Stockholm, Samariten, Promobilia and Sigurd Juselius Foundations. The study sponsors had no role in study design, collection, analysis and interpretation of data, writing of the report or in the decision to submit the report for publication.
E. Thama,b G. Nishimurac S. Geibergerd E. Horemuzovae,f D. Nilssona,b,g A. Lindstranda,b
497
Letter to the Editor A. Hammarsjöa,b M. Armenioa,b O. Mäkitiea,b,h B. Zabeli A. Nordgrena,b M. Nordenskjölda,b G. Grigelionienea,b a Department of Molecular Medicine and Surgery and Center for Molecular Medicine Karolinska Institutet Stockholm, Sweden b Department of Clinical Genetics Karolinska University Hospital Stockholm, Sweden c Department of Pediatric Imaging Tokyo Metropolitan Children’s Medical Center Tokyo, Japan d Department of Pediatric Radiology Karolinska University Hospital Stockholm, Sweden e Department of Women ́ s and Children ́ s Health Karolinska Institutet Stockholm, Sweden f Paediatric Endocrinology Unit Karolinska University Hospital Stockholm, Sweden g Science for Life Laboratory Karolinska Institutet Science Park Solna, Sweden h Folkhälsan Institute of Genetics and University of Helsinki Helsinki, Finland and i Pediatric Genetics Division, Centre for Paediatrics and
498
Adolescent Medicine Freiburg University Hospital Freiburg, Germany References 1. Nishimura G, Haga N, Kitoh H et al. The phenotypic spectrum of COL2A1 mutations. Hum Mutat 2005: 26: 36–43. 2. Hoornaert KP, Dewinter C, Vereecke I et al. The phenotypic spectrum in patients with arginine to cysteine mutations in the COL2A1 gene. J Med Genet 2006: 43: 406–413. 3. Liang G, Lian C, Huang D et al. Endoplasmic reticulum stress-unfolding protein response-apoptosis cascade causes chondrodysplasia in a col2a1 p.Gly1170Ser mutated mouse model. PLoS One 2014: 9: e86894. 4. Donahue LR, Chang B, Mohan S et al. A missense mutation in the mouse Col2a1 gene causes spondyloepiphyseal dysplasia congenita, hearing loss, and retinoschisis. J Bone Miner Res 2003: 18: 1612–1621. 5. Barat-Houari M, Dumont B, Fabre A et al. About skeletal dysplasia patients carrying two COL2A1 mutations (abstract). Milan, Italy: The European Human Genetics Conference, 2014. 6. Baker S, Booth C, Filllman C et al. A loss of function mutation in the COL9A2 gene causes autosomal recessive Stickler syndrome. Am J Med Genet 2011: 155A: 1668–1672. 7. Melkoniemi M, Brunner HG, Manouvrier S et al. Autosomal recessive disorder otospondylomegaepiphyseal dysplasia is associated with loss-of-fucntion mutations in the COL11A2 gene. Am J Hum Genet 2000: 66: 368–377.
Correspondence: G. Grigelioniene Department of Clinical Genetics Karolinska University Hospital 17176 Stockholm, Sweden. Tel.: +46 8 51773926 fax: +46 8 327734 e-mail: [email protected]
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd CLINICAL GENETICS doi: 10.1111/cge.12466
Letter to the Editor
Autosomal recessive mutations in the COL2A1 gene cause severe spondyloepiphyseal dysplasia To the Editor, Spondyloepiphyseal dysplasia congenita (SEDC, MIM 183900) is a skeletal dysplasia caused by heterozygous mutations in COL2A1, the gene encoding α1-chains of type II collagen (1). Affected individuals are disproportionately short with spinal deformities, cleft palate, myopia and hearing impairment. Skeletal surveys show platyspondyly, retarded ossification of pubic bones, epiphyseal and occasionally metaphyseal abnormalities (1). Here we report on a patient with severe SEDC and homozygosity for a novel COL2A1 mutation: p.Arg437Trp. The proband is the first child of second cousins from India with no familial history of skeletal dysplasia. He
was operated for pyloric stenosis at 1 month, and for inguinal hernia at 4 years. At 2 years of age, motor delay and short stature were noticed. Skeletal survey indicated SEDC with more severe epiphyseal dysplasia of the knees and ankles and bulbous ends of the phalanges (Fig. 1a–f). At 12 years he had severe short stature and kyphoscoliosis, a barrel-shaped chest, short neck, flat face, waddling gait, brachydactyly and myopia (−6.5/−7.5 D) with normal hearing. Auxological data are summarized in Table 1. Owing to genua valga, two corrective osteotomies were performed. The patient was on metformin treatment because of insulin resistance. The mother (36 years), father (39 years) and brother (7 years) were of average stature, had normal sight and hearing,
Fig. 1. Characteristic radiographic findings consistent with a diagnosis of severe spondyloepiphyseal dysplasia congenita (SEDC) and confirmation of the COL2A1 mutation c.1309C>T; p.Arg437Trp by Sanger sequencing. (a) Severe generalized platyspondyly with defective ossification of anterior parts of vertebral bodies in the spine (11 years). (b, c) Note that the epiphyseal dysplasia of the knee and ankle is more severe in this patient than typically seen in SEDC. Mild metaphyseal dysplasia of the lower femur and upper tibia (5 years and 3 months). (d) Short humerus with very broad bulbous metaphysis and small epiphysis (5 years and 3 months). (e) Short bulbous metacarpal bones, bulbous ends of the phalanges, and pseudoepiphysis of the second metacarpal bone. Slight shortening of the radius relative to ulna (5 years and 3 months). (f) Absence of ossification of femoral heads. Severe shortness of femoral neck. Hypoplasia of basilary portions of os ilium and of os pubis (5 years and 3 months). (g) Homozygous c.1309C>T mutation in the patient (a′ ) and heterozygous in his unaffected family members (b′ –d′ ). indicated by arrows c.1309C>T; p.Arg437Trp by Sanger sequencing.
496
Letter to the Editor Table 1. Auxology data of the patient. Midparental height (MPH) 169.15 cm (Z score −1.81). The patient had a birth weight of 3150 g and birth length of 49 cm. Height of the patient at 11 years 9 month of age was 117.5 cm Z-score Age (years) Birth 0.25 1 4 5 8 9 10 11
Difference (cm)
Z-score for difference in:
Length/height*
Weight*
Relative sitting height†
Arm span – height
Length/height – MPH
−0.78 −1.09 −2.73 −2.97 −2.67 −4.37 −4.78 −5.12 −5.56
−0.88 −1.43 −2.27 +0.42 +2.13 +3.00 +2.81 +1.94 +0.95
NA NA NA NA NA NA +5.00 +6.87 +6.70
NA NA NA NA NA NA +1.4 +2.0 +1.1
+1.03 +0.72 −0.92 −1.16 −0.86 −2.56 −2.97 −3.31 −3.75
NA, not available. *Z-score for weight and height at birth and at follow up are based on Swedish standards from Albertsson Wikland K, Luo Z, Niklassson A et al. Swedish population-based longitudinal reference values from birth to 18 years of age for height, weight and head circumference. Acta Pediatrica 2002: 91: 739–754. †Z-scores for relative sitting height are calculated according to Dutch standards from Fredriks A, van Buuren S, van Heel W et al. Nationwide references for sitting height, leg length and sitting height/height ratio and their diagnostic value for disproportionate growth disorders. Archives Disease Childhood 2005: 90 (Suppl. 1): 55–65.
no joint pain or palatal abnormalities. The father suffers from multiple mandibular and patellar luxations. Skeletal surveys of both parents were normal. The patient was homozygous for a novel variant in COL2A1: NM_001844 c.1309C > T (exon 21), p.Arg437Trp. The variant was predicted to be damaging by SIFT, Align GVGD, and PolyPhen2 and alters a highly conserved nucleotide and amino acid, replacing a positively charged polar arginine with an aromatic and hydrophobic tryptophan. c.1309C>T has not been reported in healthy individuals in 135 local exomes, the 1000 genomes browser, ClinVar, dbSNP v137, or ESP6500. Extended testing was performed with: whole exome sequencing using TruSeq (Illumina, San Diego, CA) with 94–96% ×10 coverage; comparative genome hybridization array (array-CGH with a resolution of 50 kb) (Agilent Technologies, Paulo Alto, CA); and a high resolution targeted array-CGH for 226 known skeletal dysplasia genes, including COL2A1. No other disease causing genetic abnormalities were revealed. The parents and the brother were heterozygous for the COL2A1 mutation (Fig. 1g). Heterozygous mutations in COL2A1 give rise to a wide range of disorders including SEDC and there is limited genotype–phenotype correlation (1). Most mutations in COL2A1 involve the triple helix domain. The majority affect a glycine required for correct conformation of the triple helix and exert a dominant negative effect, leading to severe phenotypes (achondrogenesis, hypochondrogenesis and SEDC) (1). Arginine to cysteine substitutions are generally milder causing spondyloarthropathy and Stickler syndrome, but rarely SEDC (2). Non-glycine, non-cysteine missense mutations in the COL2A1 gene constitute only 2% of reported missense mutations and are associated with milder phenotypes (https://grenada.lumc.nl/LOVD2/ mendelian_genes/home.php?select_db=COL2A1). We
hypothesize that the p.Arg437Trp is even milder, with no clinically evident effect in the heterozygous state. Mouse homozygous for col2a1 mutations usually succumb perinatally (3). However, mice homozygous for p.Arg1417Cys mutation in col2a1 are viable with skeletal dysplasia, retinal abnormalities and hearing loss (4). This mouse model shows that specific homozygous mutations in COL2A1 are compatible with life. This is further supported by the recent conference report on five patients with possible autosomal recessive COL2A1 mutations (5). Additionally, autosomal recessive mutations have been reported in collagens IX and XI that covalently interact with collagen II (6, 7). In conclusion, our finding of biallelic mutations in the COL2A1 gene as a cause for severe SEDC is in line with observations in other collagenopathies, and extends the genetic and phenotypic spectrum of COL2A1-related disorders. Acknowledgements We are grateful to the patient and his family for participation and associated professor Lars Hagenäs for discussions. Financial support was provided through the regional agreement on medical training and clinical research (ALF) between Stockholm County Council and Karolinska Institutet, the Swedish Research Council, and, in addition, by grants from Kronprinsessan Lovisas and Axel Tiellmans Minnesfond, Frimurare Barnhuset i Stockholm, Samariten, Promobilia and Sigurd Juselius Foundations. The study sponsors had no role in study design, collection, analysis and interpretation of data, writing of the report or in the decision to submit the report for publication.
E. Thama,b G. Nishimurac S. Geibergerd E. Horemuzovae,f D. Nilssona,b,g A. Lindstranda,b
497
Letter to the Editor A. Hammarsjöa,b M. Armenioa,b O. Mäkitiea,b,h B. Zabeli A. Nordgrena,b M. Nordenskjölda,b G. Grigelionienea,b a Department of Molecular Medicine and Surgery and Center for Molecular Medicine Karolinska Institutet Stockholm, Sweden b Department of Clinical Genetics Karolinska University Hospital Stockholm, Sweden c Department of Pediatric Imaging Tokyo Metropolitan Children’s Medical Center Tokyo, Japan d Department of Pediatric Radiology Karolinska University Hospital Stockholm, Sweden e Department of Women ́ s and Children ́ s Health Karolinska Institutet Stockholm, Sweden f Paediatric Endocrinology Unit Karolinska University Hospital Stockholm, Sweden g Science for Life Laboratory Karolinska Institutet Science Park Solna, Sweden h Folkhälsan Institute of Genetics and University of Helsinki Helsinki, Finland and i Pediatric Genetics Division, Centre for Paediatrics and
498
Adolescent Medicine Freiburg University Hospital Freiburg, Germany References 1. Nishimura G, Haga N, Kitoh H et al. The phenotypic spectrum of COL2A1 mutations. Hum Mutat 2005: 26: 36–43. 2. Hoornaert KP, Dewinter C, Vereecke I et al. The phenotypic spectrum in patients with arginine to cysteine mutations in the COL2A1 gene. J Med Genet 2006: 43: 406–413. 3. Liang G, Lian C, Huang D et al. Endoplasmic reticulum stress-unfolding protein response-apoptosis cascade causes chondrodysplasia in a col2a1 p.Gly1170Ser mutated mouse model. PLoS One 2014: 9: e86894. 4. Donahue LR, Chang B, Mohan S et al. A missense mutation in the mouse Col2a1 gene causes spondyloepiphyseal dysplasia congenita, hearing loss, and retinoschisis. J Bone Miner Res 2003: 18: 1612–1621. 5. Barat-Houari M, Dumont B, Fabre A et al. About skeletal dysplasia patients carrying two COL2A1 mutations (abstract). Milan, Italy: The European Human Genetics Conference, 2014. 6. Baker S, Booth C, Filllman C et al. A loss of function mutation in the COL9A2 gene causes autosomal recessive Stickler syndrome. Am J Med Genet 2011: 155A: 1668–1672. 7. Melkoniemi M, Brunner HG, Manouvrier S et al. Autosomal recessive disorder otospondylomegaepiphyseal dysplasia is associated with loss-of-fucntion mutations in the COL11A2 gene. Am J Hum Genet 2000: 66: 368–377.
Correspondence: G. Grigelioniene Department of Clinical Genetics Karolinska University Hospital 17176 Stockholm, Sweden. Tel.: +46 8 51773926 fax: +46 8 327734 e-mail: [email protected]
