Haeringen, Arie van

ABSTRACT Background Chondrodysplasia punctata 1 (CDPX1) is an X‐linked recessive disorder of cartilage and bone development characterized by stippling on the cartilage and bone, flattened nasal bridge, and brachydactyly, or short fingers. CDPX1 has been associated with variants in the ARSL gene and is known to manifest prenatally, however, there has been no systematic literature review on this evidence. Aims Here, we reviewed the current literature on prenatal manifestations of CDPX1, and additionally introduce previously unpublished cases. Materials & Methods A systematic review of the literature was performed. Additionally, a GeneMatcher submission was created and a call for cases was presented at the Fetal Sequencing Consortium meetings to find previously unpublished cases. Results For the 22 fetuses reported here, we found that 55% had nasal hypoplasia, 41% had bony stippling or calcifications, 32% had polyhydramnios, 5% had oligohydramnios, 23% had shortened long bones, 23% had spinal canal stenosis, 18% had ventriculomegaly, 9% had brachydactyly/brachytelephalangy, 9% had clubbed feet, 9% had premature rupture of membranes, and 9% had intraventricular hemorrhage detected through sonography or radiography. We also found 17 unique variants in ARSL for these 22 fetuses. Discussion A previously unpublished association of ARSL variants with intrauterine fetal death or stillbirth has been noted in this study. It is also possible that intracranial hemorrhage is an underrecognized feature associated with CDPX1 variation. However, there have been challenges in applying ACMG criteria to ARSL, a gene without an associated Variant Curation Expert Panel. Conclusion This literature review and case series highlights which features of CDPX1 manifest prenatally, as well as introduces new phenotypes that have not been previously identified.

Pathogenic variants in KMT5B , a lysine methyltransferase, are associated with global developmental delay, macrocephaly, autism, and congenital anomalies (OMIM # 617788). Given the relatively recent discovery of this disorder, it has not been fully characterized. Deep phenotyping of the largest ( n = 43) patient cohort to date identified that hypotonia and congenital heart defects are prominent features that were previously not associated with this syndrome. Both missense variants and putative loss-of-function variants resulted in slow growth in patient-derived cell lines. KMT5B homozygous knockout mice were smaller in size than their wild-type littermates but did not have significantly smaller brains, suggesting relative macrocephaly, also noted as a prominent clinical feature. RNA sequencing of patient lymphoblasts and Kmt5b haploinsufficient mouse brains identified differentially expressed pathways associated with nervous system development and function including axon guidance signaling. Overall, we identified additional pathogenic variants and clinical features in KMT5B -related neurodevelopmental disorder and provide insights into the molecular mechanisms of the disorder using multiple model systems.