Identification of two CUL7 variants in two Chinese families with 3-M syndrome by whole-exome sequencing

Further phenotypic features and two novel POC1A variants in a patient with SOFT syndrome: A case report

Short stature, onychodysplasia, facial dysmorphism and hypotrichosis (SOFT) syndrome is a rare autosomal recessive disease caused by POC1 centriolar protein A (POC1A) pathogenic variants. However, knowledge of genotypic and phenotypic features of SOFT syndrome remain limited as few families have been examined; therefore, the clinical identification of SOFT syndrome remains a challenge. The aim of the present case report was to investigate the genetic cause of this syndrome in a patient with a short stature, unusual facial appearance, skeletal dysplasia and sparse body hair. Giemsa banding and exome sequencing were performed to investigate the genetic background of the family. Spiral computed tomography and magnetic resonance imaging were used for investigating further phenotypic features of the patient. Exome sequencing identified that POC1A had two compound heterozygous variants, namely c.850_851insG and c.593_605delGTGGGACGTGCAT, which, to the best of our knowledge, have not been reported elsewhere. Novel phenotypes were also identified as follows: i) Metaphyseal dysplasia was alleviated (and/or even disappeared) with age; ii) the density of the femoral neck was uneven and the hyperintensity signal of the metaphysis was stripe‑like. Thus, the present case report expands the knowledge regarding phenotypic and genotypic features of SOFT syndrome.

Identification of two CUL7 variants in two Chinese families with 3-M syndrome by whole-exome sequencing

Background

3‐M syndrome is a rare autosomal recessive disorder characterized by primordial growth retardation, large head circumference, characteristic facial features, and mild skeletal changes, which is associated with the exclusive variants in three genes, namely CUL7, OBSL1, and CCDC8. Only a few 3‐M syndrome patients have been reported in Chinese population.

Methods

Children with unexplained severe short stature, facial dysmorphism, and normal intelligence in two Chinese families and their relatives were enrolled. Trio‐whole‐exome sequencing (trio‐WES) and pathogenicity prediction analysis were conducted on the recruited patients. A conservative analysis of the mutant amino acid sequences and function prediction analysis of the wild‐type (WT) and mutant CUL7 protein were performed.

Results

We identified a homozygous missense variant (NM_014780.4: c.4898C > T, p.Thr1633Met) in CUL7 gene in a 6‐month‐old female infant from a non‐consanguineous family, and a homozygous frameshift variant (NM_014780.4: c.3722_3749 dup GGCTGGCACAGCTGCAGCAATGCCTGCA, p. Val1252Glyfs*23) in CUL7 gene in two affected siblings from a consanguinity family. These two variants may affect the properties and structure of CUL7 protein.

Conclusion

These two rare variants were observed in Chinese population for the first time and have not been reported in the literature. Our findings expand the variant spectrum of 3‐M syndrome in Chinese population and provide valuable insights into the early clinical manifestations and pathogenesis of 3‐M syndrome for pediatricians and endocrinologists.