Congenital anomalies affect 3% of live births and are associated with higher rates of fetal demise. In the majority of cases, the underlying cause is unknown. In order to identify novel genetic causes of congenital anomalies, we have undertaken exome and whole genome sequencing of patient cohorts with either vertebral anomalies or congenital heart disease.
We identified two novel heterozygous stop gain variants in the WBP11 gene in unrelated patients with the cervical vertebral anomaly Klippel-Feil Syndrome. WBP11 encodes an evolutionarily conserved activator of splicing, which has not been previously linked to human disease. Ten additional patients from five families were identified via GeneMatcher, four families with heterozygous truncating WBP11 variants and one with a predicted pathogenic variant in WBP11. Although patient phenotypes varied, common malformations included cervical vertebral fusions, oesophageal atresia, kidney and heart anomalies. We generated a mouse model of WBP11 heterozygosity by CRISPR-Cas9 targeting. Mice heterozygous for a Wbp11 null allele were not found in the expected Mendelian ratio with many dying either late in gestation, postnatally or as adults. Defects of the axial skeleton, oesophagus and kidneys were found in Wbp11 heterozygous mice, similar to affected individuals, confirming WBP11 mutation as a cause of multiple congenital anomalies in humans and mice (1).
Efforts such as this to characterise developmental defects in mouse models of human congenital disease are hampered by the conventional qualitative approach. The recently published LAMA automated phenotyping pipeline addresses this issue by generating quantitative volumetric data from embryo micro-CT scans (2). We have extended the LAMA pipeline to include additional developmental stages (E12.5 and E17.5). LAMA analysis demonstrates that compared to WT embryos, Wbp11+/- embryos are significantly smaller as are their cervical vertebrae and kidneys. LAMA identified other significant differences including the aortic vessels, highlighting a right aortic arch defect in Wbp11+/- embryos previously overlooked by manual analysis. These findings highlight the advantages of the quantitative volumetric analysis approach taken by the LAMA pipeline.