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[Identification of a novel missense variant of the KAT6B gene in a child with Say-Barber-Biesecker-Young-Simpson syndrome].

OBJECTIVE
To explore the genetic basis for a child suspected for Say-Barber-Biesecker-Young-Simpson syndrome.


METHODS
Genomic DNA was extracted from peripheral blood samples of the child and her parents. Whole exome sequencing was carried out for the proband. Suspected variants were validated by Sanger sequencing. The impact of the variants was predicted by bioinformatic analysis.


RESULTS
The child was found to harbor a de novo missense variant c.2623C>T (p.Asp875Tyr) in exon 13 of the KAT6B gene. The variant was previously unreported, and was not recorded in the major allele frequency database and predicted to be pathogenic based on PolyPhen-2, MutationTaster and PROVEAN analysis. As predicted by UCSF chimera and CASTp software, the variant can severely impact the substrate-binding pocket of histone acetyltransferase, resulting in loss of its enzymatic activity. Based on standards and guidelines by the American College of Medical Genetics and Genomics, the variant was classified to be likely pathogenic (PS2+PM2+PP3).


CONCLUSION
The child's condition may be attributed to the de novo missense c.2623C>T (p.Asp875Tyr) variant of the KAT6B gene.