Spectrum of candidate gene mutations associated with Indian familial oculocutaneous and ocular albinism.

PURPOSE

Albinism is a group of genetic disorders, showing a broad spectrum of different phenotypes. The purpose of this study was to screen known candidate genes for oculocutaneous albinism (OCA) and ocular albinism (OA) mutations in Indian patients.

METHODS

Blood samples were collected from 23 probands and 13 affected family members from 23 genetically unrelated Indian families (22 diagnosed as OCA and 1 diagnosed as OA) and analyzed by bidirectional DNA sequencing of the classic OCA genes--tyrosinase (TYR, or oculocutaneous albinism IA), pink eyed dilution (P; or oculocutaneous albinism II (OCA2]), tyrosinase-related protein 1 (TYRP1), solute carrier family 45, member 2 (SLC45A2; or membrane-associated transporter protein [MATP])--and the OA1 gene, G protein-coupled receptor 143 (GPR143).

RESULTS

Three missense mutations, c. 715 C>T (R239W), c. 896 G>A (R299H), c.1255 G>A (G419R), and one termination c. 832 C>T (R278X), were identified in TYR, as well as one novel mutation, c.1453 G>A (G485R) in P. One novel single nucleotide polymorphism (SNP) was identified in both TYR and P; few reported SNPs were identified. The G>A base substitution caused relatively conservative amino acid changes, which altered glycine to arginine residues within the topological domain. The novel OCA2 mutation was not present in 100 control samples. This study identified two probands carrying mutations alone, 16 probands carrying SNPs alone, 4 probands carrying both mutations and SNPs and only one proband carrying neither mutations nor SNPs.

CONCLUSIONS

Although sequence analysis was performed with all five candidate genes, only four (17.39%) of the 23 probands showed mutations in TYR and 2 probands (8.69%) showed an unreported novel mutation in P. Genetic counseling for phenotypical diagnosis and genetic mutation screening of these genes will help to minimize the incidence of OCA and OA in future generations.