Clinical and molecular characterization of four patients with Robinow syndrome from different families

In-Depth Genomic Analysis: The New Challenge in Congenital Heart Disease

The use of next-generation sequencing has provided new insights into the causes and mechanisms of congenital heart disease (CHD). Examinations of the whole exome sequence have detected detrimental gene variations modifying single or contiguous nucleotides, which are characterised as pathogenic based on statistical assessments of families and correlations with congenital heart disease, elevated expression during heart development, and reductions in harmful protein-coding mutations in the general population. Patients with CHD and extracardiac abnormalities are enriched for gene classes meeting these criteria, supporting a common set of pathways in the organogenesis of CHDs. Single-cell transcriptomics data have revealed the expression of genes associated with CHD in specific cell types, and emerging evidence suggests that genetic mutations disrupt multicellular genes essential for cardiogenesis. Metrics and units are being tracked in whole-genome sequencing studies.

A novel frameshift mutation of DVL1-induced Robinow syndrome: A case report and literature review

BACKGROUND

Robinow syndrome is a rare genetic disorder that affects the development of multiple systems. Due to its low prevalence and diversity of phenotypic presentation it has been challenging to definitively characterize features of Robinow syndrome.

METHODS

We performed DNA extraction, whole-exome sequencing analysis, and mutation analysis of DVL1 to obtain genetic data on the patient. We subsequently analyzed the patient's clinical and genetic data.

RESULTS

The proband was a 3-month-old female infant who suffered from significant global developmental delay and metabolic disorder. The main clinical manifestations included facial dysmorphisms, bilateral dislocation of the hip joint, and hearing impairment. Whole-exome sequencing of the patient's DNA revealed a heterozygous mutation of c.1620delC in DVL1. Analysis with the MutationTaster application indicated that both were pathogenic (probability = 1), causing frameshift mutations affecting 107 amino acids (p.S542Vfs*107). Significant structural changes were identified in the amino acid sequence after the WNT signaling-related DEP domain site was predicted using the AlphaFold Protein structure database. The stability of the three main domains was then evaluated using SWISS-MODEL, and indicated that the mutation did not alter the DIX, PDZ, or DEP domain sequences. Because all reported pathogenic mutations were located near the DEP domain, we speculated that structural changes around the DEP domain may have impaired WNT domain function and WNT signaling, resulting in Robinow syndrome.

CONCLUSION

The present case suggests that molecular genetic screening is useful for the diagnosis of developmental disorders, particularly in children with a positive family history. In the current patient all the related pathological variants were located within a narrow locus. This report expands the known manifestations of Robinow syndrome and contributes to refinement of its molecular basis.

Novel pathogenic variants and quantitative phenotypic analyses of Robinow syndrome: WNT signaling perturbation and phenotypic variability

Robinow syndrome (RS) is a genetically heterogeneous disorder with six genes that converge on the WNT/planar cell polarity (PCP) signaling pathway implicated (DVL1, DVL3, FZD2, NXN, ROR2, and WNT5A). RS is characterized by skeletal dysplasia and distinctive facial and physical characteristics. To further explore the genetic heterogeneity, paralog contribution, and phenotypic variability of RS, we investigated a cohort of 22 individuals clinically diagnosed with RS from 18 unrelated families. Pathogenic or likely pathogenic variants in genes associated with RS or RS phenocopies were identified in all 22 individuals, including the first variant to be reported in DVL2. We retrospectively collected medical records of 16 individuals from this cohort and extracted clinical descriptions from 52 previously published cases. We performed Human Phenotype Ontology (HPO) based quantitative phenotypic analyses to dissect allele-specific phenotypic differences. Individuals with FZD2 variants clustered into two groups with demonstrable phenotypic differences between those with missense and truncating alleles. Probands with biallelic NXN variants clustered together with the majority of probands carrying DVL1, DVL2, and DVL3 variants, demonstrating no phenotypic distinction between the NXN-autosomal recessive and dominant forms of RS. While phenotypically similar diseases on the RS differential matched through HPO analysis, clustering using phenotype similarity score placed RS-associated phenotypes in a unique cluster containing WNT5A, FZD2, and ROR2 apart from non-RS-associated paralogs. Through human phenotype analyses of this RS cohort and OMIM clinical synopses of Mendelian disease, this study begins to tease apart specific biologic roles for non-canonical WNT-pathway proteins.