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Spondyloepiphyseal dysplasia congenita (SEDC) is a severe non-lethal type 2 collagenopathy caused by pathogenic variants in the COL2A1 gene, which encodes the alpha-1 chain of type II collagen. SEDC is clinically characterized by severe short stature, degenerative joint disease, hearing impairment, orofacial anomalies and ocular manifestations. To study and therapeutically target the underlying disease mechanisms, human iPSC-chondrocytes are considered highly suitable as they have been shown to exhibit several key features of skeletal dysplasias. Prior to creating iPSC-chondrocytes, peripheral blood mononuclear cells of two male SEDC patients, carrying the p.Gly1107Arg and p.Gly408Asp pathogenic variants, respectively, were successfully reprogrammed into iPSCs using the CytoTune™-iPS 2.0 Sendai Kit (Invitrogen)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Marfan syndrome (MFS) is a connective tissue disorder with pleiotropic manifestations in the ocular, skeletal and cardiovascular system; and is typically cause by pathogenic variants in the fibrillin-1 (FBN1) gene. We report a generated induced pluripotent cell (iPSC) line of a MFS patient with an FBN1 c.7754T > C (p.Ile2585Thr) variant. The cell line was generated from peripheral blood mononuclear cells (PBMCs) and after reprogramming the line showed a no relevant copy number alterations, expression of pluripotency markers and was able to differentiate into three germ layers while carrying the original genotype., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Hemizygous missense variants in the X-linked BGN gene, encoding the extracellular matrix protein biglycan, cause spondyloepimetaphyseal dysplasia (SEMD, biglycan type), which is clinically characterized by short stature, brachydactyly and osteoarthritis. Little is known about the pathomechanisms underlying SEMD, biglycan type. IPSC-derived chondrocyte disease models have been shown to exhibit several key aspects of known disease mechanisms of skeletal dysplasias and are therefore considered highly suitable human disease models to study SEMD, biglycan type. Prior to creating iPSC-chondrocytes, dermal fibroblasts of two male patients with SEMD, biglycan type, carrying the p.Gly259Val variant were successfully reprogrammed into iPSCs using the CytoTune TM -iPS 2.0 Sendai Kit (Invitrogen)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Meester-Loeys syndrome (MRLS) is an X-linked syndromic form of thoracic aortic aneurysm and dissection. Here, we report an iPSC line (BBANTWi009-A) of a boy carrying a hemizygous BGN mutation (chrX:153502980-153530518del, GRCh38) causing MRLS. iPSCs were generated from dermal fibroblasts by reprogramming with the Cytotune®-iPS 2.0 Sendai Reprogramming Kit (Invitrogen). The generated iPSCs showed a normal karyotype, expressed pluripotency markers, were differentiated into the three germ layers and carried the original genotype., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Purpose: CTR9 is a subunit of the PAF1 complex (PAF1C) that plays a crucial role in transcription regulation by binding CTR9 to RNA polymerase II. It is involved in transcription-coupled histone modification through promoting H3K4 and H3K36 methylation. We describe the clinical and molecular studies in 13 probands, harboring likely pathogenic CTR9 missense variants, collected through GeneMatcher., Methods: Exome sequencing was performed in all individuals. CTR9 variants were assessed through 3-dimensional modeling of the activated human transcription complex Pol II-DSIF-PAF-SPT6 and the PAF1/CTR9 complex. H3K4/H3K36 methylation analysis, mitophagy assessment based on tetramethylrhodamine ethyl ester perchlorate immunofluorescence, and RNA-sequencing in skin fibroblasts from 4 patients was performed., Results: Common clinical findings were variable degrees of intellectual disability, hypotonia, joint hyperlaxity, speech delay, coordination problems, tremor, and autism spectrum disorder. Mild dysmorphism and cardiac anomalies were less frequent. For 11 CTR9 variants, de novo occurrence was shown. Three-dimensional modeling predicted a likely disruptive effect of the variants on local CTR9 structure and protein interaction. Additional studies in fibroblasts did not unveil the downstream functional consequences of the identified variants., Conclusion: We describe a neurodevelopmental disorder caused by (mainly) de novo variants in CTR9, likely affecting PAF1C function., Competing Interests: Conflict of Interest Amber Begtrup is an employee of GeneDx, Inc. Stylianos E. Antonarakis and Emmanuelle Ranza are cofounders of MediGenome. All other authors declare no conflicts of interest., (Copyright © 2022 American College of Medical Genetics and Genomics. Published by Elsevier Inc. All rights reserved.)

Purpose: In a large cohort of 373 pediatric patients with Marfan syndrome (MFS) with a severe cardiovascular phenotype, we explored the proportion of patients with MFS with a pathogenic FBN1 variant and analyzed whether the type/location of FBN1 variants was associated with specific clinical characteristics and response to treatment. Patients were recruited on the basis of the following criteria: aortic root z-score > 3, age 6 months to 25 years, no prior or planned surgery, and aortic root diameter < 5 cm., Methods: Targeted resequencing and deletion/duplication testing of FBN1 and related genes were performed., Results: We identified (likely) pathogenic FBN1 variants in 91% of patients. Ectopia lentis was more frequent in patients with dominant-negative (DN) variants (61%) than in those with haploinsufficient variants (27%). For DN FBN1 variants, the prevalence of ectopia lentis was highest in the N-terminal region (84%) and lowest in the C-terminal region (17%). The association with a more severe cardiovascular phenotype was not restricted to DN variants in the neonatal FBN1 region (exon 25-33) but was also seen in the variants in exons 26 to 49. No difference in the therapeutic response was detected between genotypes., Conclusion: Important novel genotype-phenotype associations involving both cardiovascular and extra-cardiovascular manifestations were identified, and existing ones were confirmed. These findings have implications for prognostic counseling of families with MFS., Competing Interests: Conflict of Interest The authors declare no conflicts of interest., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)