Locus heterogeneity characterizes a variety of skeletal dysplasias often due to interacting or overlapping signaling pathways. Robinow syndrome is a skeletal disorder historically refractory to molecular diagnosis, potentially stemming from substantial genetic heterogeneity. All current known pathogenic variants reside in genes within the noncanonical Wnt signaling pathway including ROR2, WNT5A, and more recently, DVL1 and DVL3. However, $70% of autosomal-dominant Robinow syndrome cases remain molecularly unsolved. To investigate this missing heritability, we recruited 21 families with at least one family member clinically diagnosed with Robinow or Robinow-like phenotypes and performed genetic and genomic studies. In total, four families with variants in FZD2 were identified as well as three individuals from two families with biallelic variants in NXN that co-segregate with the phenotype. Importantly, both FZD2 and NXN are relevant protein partners in the WNT5A interactome, supporting their role in skeletal development. In addition to confirming that clustered -1 frameshifting variants in DVL1 and DVL3 are the main contributors to dominant Robinow syndrome, we also found likely pathogenic variants in candidate genes GPC4 and RAC3, both linked to the Wnt signaling pathway. These data support an initial hypothesis that Robinow syndrome results from perturbation of the Wnt/PCP pathway, suggest specific relevant domains of the proteins involved, and reveal key contributors in this signaling cascade during human embryonic development. Contrary to the view that non-allelic genetic heterogeneity hampers gene discovery, this study demonstrates the utility of rare disease genomic studies to parse gene function in human developmental pathways.

Purpose: Exome sequencing (ES) is increasingly used for the diagnosis of rare genetic disease. However, some pathogenic sequence variants within the exome go undetected due to the technical difficulty of identifying them. Mobile element insertions (MEIs) are a known cause of genetic disease in humans but have been historically difficult to detect via ES and similar targeted sequencing methods. Methods: We developed and applied a novel MEI detection method prospectively to samples received for clinical ES beginning in November 2017. Positive MEI findings were confirmed by an orthogonal method and reported back to the ordering provider. In this study, we examined 89,874 samples from 38,871 cases. Results: Diagnostic MEIs were present in 0.03% (95% binomial test confidence interval: 0.02-0.06%) of all cases and account for 0.15% (95% binomial test confidence interval: 0.08-0.25%) of cases with a molecular diagnosis. One diagnostic MEI was a novel founder event. Most patients with pathogenic MEIs had prior genetic testing, three of whom had previous negative DNA sequencing analysis of the diagnostic gene. Conclusion: MEI detection from ES is a valuable diagnostic tool, reveals molecular findings that may be undetected by other sequencing assays, and increases diagnostic yield by 0.15%.

Somatic variants in tumor necrosis factor receptor-associated factor 7 (TRAF7) cause meningioma and other cancers, while germline variants have recently been identified in seven patients with a syndrome associating cardiac, facial and digital anomalies with developmental delay. We aimed to define the clinical and mutational spectrum associated with TRAF7 germline variants through identification and description of 45 new patients, and to determine the effects of the variants at a molecular level through transcriptomic analysis of patient fibroblasts.Methods We performed exome, targeted capture and Sanger sequencing in a series of patients with undiagnosed developmental disorders. Phenotypic and mutational comparisons Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation We hope you will consider our manuscript for publication in Genetics in Medicine and we look forward to hearing your response.

The list of Mendelian disorders of the epigenetic machinery has expanded rapidly during the last five years. A few missense variants in the chromatin remodeler CHD1 have been found in several large scale sequencing efforts focused on uncovering the genetic etiology of autism. Here we describe CHD1 heterozygous missense variants in a cohort of patients with autism, speech apraxia, developmental delay and facial dysmorphic features. Importantly three of these variants occurred de novo. We also report on a patient with a de novo deletion covering a large fraction of the CHD1 gene without any obvious neurological phenotype. Our results suggest that variants in CHD1 can lead to diverse phenotypic outcomes; however, the neurodevelopmental phenotype appears to be limited to patients with missense variants, which is compatible with a dominant negative mechanism of disease.