NGS-based targeted sequencing identified two novel variants in Southwestern Chinese families with oculocutaneous albinism

Abstract

Background: Oculocutaneous albinism (OCA) is a group of heterogeneous genetic diseases characterized by a reduction or complete lack of pigmentation in the hair, skin, and eyes. It is associated with reduced visual acuity, nystagmus, photophobia, and strabismus. OCA type 1 (OCA1) and type 2 (OCA2) are caused by mutations in the tyrosinase (TYR) and OCA2 genes, which are responsible for most cases of OCA. The present study aimed to identify the mutational spectra of 18 southwest Chinese probands with OCA.

Results: We used a skin disease-targeted panel to sequence more than 400 genes, including 23 genes (TYR, OCA2, AP3B1, BLOC1S3, BLOC1S6, C10orf11, DTNBP1, FRMD7, GPR143, HPS1, HPS3, HPS4, HPS5, HPS6, LYST, MC1R, MITF, MLPH, MYO5A, RAB27A, SLC24A5, SLC45A2, TYRP1) associated with syndromic and non-syndromic albinism. The targeted panel was applied to 18 patients from southwest China, nine (50%) patients were diagnosed with OCA1, and nine (50%) were diagnosed with OCA2. Our data indicate that OCA1 and OCA2, the most common subtypes, probably have the same prevalence in southwest China. In total, we identified 26 variants in TYR and OCA2 from 18 OCA cases using the NGS technology, including 24 variants presented in the Human Gene Mutation Database Professional (HGMD) and two novel variants, c.559_560insCATTATTATGTGTCAAATTATCCCC in TYR and c.1514 T > C in OCA2, which have not been previously reported. According to the American College of Medical Genetics and Genomics (ACMG) classification, c.559_560insCATTATTATGTGTCAAATTATCCCC (p.G190Cfs*12) is classified as a pathogenic variant, and c.1514 T > C (p.F505S) is evaluated as a likely pathogenic variant.

Conclusions: Two novel variants were identified which will expand the mutational spectra of TYR and OCA2. The results of the present study may have implications for genetic counseling, carrier screening, and clinical management of the disease.

Keywords: Medical genomics; Nucleotide variations; OCA2; Oculocutaneous albinism; TYR; Targeted NGS.

Fig. 1

A A picture of an OCA patient (Patient.5 in Table 1) with creamy white skin color and white hair color. B A pedigree drawing of Sanger sequencing of the OCA patient. The girl inherited the c.1346A > G and c.559_560insCATTATTATGTGTCAAATTATCCCC from father and mother, respectively. C The p.G190 in TYR is highly conserved amino acids throughout evolution

Fig. 2

A A picture of an OCA patient (Patient.13 in Table 1) with white skin color and white hair color. B A pedigree drawing of Sanger sequencing of the OCA patient. The girl inherited the c.1349C > T and c.1514 T > C from father and mother, respectively. C The p.F505 in OCA2 is highly conserved amino acids throughout evolution. D Modeling of the amino acids conformation changes by SWISS-MODEL