A de novo TRPV4 variant c.2479C>G (p.Pro827Ala) in Spondylometaphyseal dysplasia Kozlowski type: identification and functional analysis.

Spondylometaphyseal dysplasia, Kozlowski type (SMDK), is an autosomal dominant skeletal disorder characterized by abnormalities of the spine, metaphyses and epiphyses. It is associated with variants in TRPV4, although the underlying molecular mechanisms remain unclear. A de novo heterozygous TRPV4 variant (c.2479C>G, p.Pro827Ala) was detected in a patient with SMDK by whole-exome sequencing, and transcriptome sequencing was performed in available family members. Expression analyses showed reduced TRPV4 transcript and protein levels associated with the p.Pro827Ala variant. Cellular functional assays further showed decreased intracellular Ca2+ concentrations without detectable changes in plasma membrane localization. In addition, ATP2B1 and PRKCQ were downregulated. To further investigate the pathogenic mechanism, a heterozygous knock-in Trpv4P827A/+ mouse model was generated using CRISPR/Cas9. Trpv4P827A/P827A homozygous mice exhibited significant skeletal developmental delay, and transcriptome profiling revealed dysregulated expression of homeobox, zf_C2H2, and forkhead transcription factor families during early development. Collectively, these findings expand the spectrum of pathogenic TRPV4 variants and provide mechanistic insights into the pathogenic effect of TRPV4 p.Pro827Ala in SMDK, supporting improved clinical diagnosis and future functional studies.