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Clinical expression of Ellis-van Creveld syndrome (EvC) is variable and mild phenotypes have been described, including patients with mostly cardiac and limb involvement. Whether these cases are part of the EvC phenotypic spectrum or separate conditions is disputed. Herein, we describe a family with vertical transmission of atrioventricular canal defect (AVCD), common atrium, and postaxial polydactyly. Targeted sequencing of EVC, EVC2, WDR35, DYNC2LI1, and DYNC2H1 identified different compound heterozygosity in EVC genotypes in the two affected members, consisting of a nonsense (p.Arg622Ter) and a missense (p.Arg663Pro) variant in the father, and the same nonsense variant and a noncanonical splice-site in-frame change (c.1316-7A>G) in the daughter. Complementary DNA sequencing, immunoblot, and immunofluorescence experiments using patient-derived fibroblasts and Evc -/- mouse embryonic fibroblasts showed that p.Arg622Ter is a loss-of-function mutation, whereas p.Arg663Pro and the splice-site change c.1316-7A>G are hypomorphic variants resulting in proteins that retain, in part, the ability to complex with EVC2. Our molecular and functional data demonstrate that at least in some cases the condition characterized as "common atrium/AVCD with postaxial polydactyly" is a mild form of EvC due to hypomorphic EVC mutations, further supporting the occurrence of genotype-phenotype correlations in this syndrome., (© 2020 Wiley Periodicals LLC.)

Atrioventricular septal defect (AVSD) may occur as part of a complex disorder (e.g., Down syndrome, heterotaxy), or as isolate cardiac defect. Multiple lines of evidence support a role of calcineurin/NFAT signaling in AVSD, and mutations in CRELD1, a protein functioning as a regulator of calcineurin/NFAT signaling have been reported in a small fraction of affected subjects. In this study, 22 patients with isolated AVSD and 38 with AVSD and heterotaxy were screened for NFATC1 gene mutations. Sequence analysis identified three missense variants in three individuals, including a subject with isolated AVSD [p.(Ala367Val)], an individual with AVSD and heterotaxy [p.(Val210Met)], and a subject with AVSD, heterotaxy, and oculo-auriculo-vertebral spectrum (OAVS) [p.(Ala696Thr)], respectively. The latter was also heterozygous for a missense change in TBX1 [p.(Pro86Leu)]. Targeted resequencing of genes associated with AVSD, heterotaxy, or OAVS excluded additional hits in the three mutation-positive subjects. Functional characterization of NFATC1 mutants documented defective nuclear translocation and decreased transcriptional transactivation activity. When expressed in zebrafish, the three NFATC1 mutants caused cardiac looping defects and altered atrioventricular canal patterning, providing evidence of their functional relevance in vivo. Our findings support a role of defective NFATC1 function in the etiology of isolated and heterotaxy-related AVSD., (© 2018 Wiley Periodicals, Inc.)