Identification of two Missense Mutations (p.Ile198Thr & p.Ser44Arg) in TYR gene in Pakistani families

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Research Paper 01/04/2017
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Identification of two Missense Mutations (p.Ile198Thr & p.Ser44Arg) in TYR gene in Pakistani families

Muhammad Luqman, Asma Yousafzai, Nisar Ahmed, Asad Ullah, Riaz-ul-Amin, Abdul Hameed Baloch, Sara Naudhani, Shakeela Daud
Int. J. Biosci.10( 4), 232-238, April 2017.
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Oculocutaneous albinism (OCA) is an autosomal recessive disorder. The most common type oculocutaneous albinism type 1 (OCA1) is caused by tyrosinase (TYR) gene. Biosynthesis of melanin in human are controlled by Tyrosinase enzyme, which is encoded by gene TYR present on 11q14.3 chromosome. TYR gene is expressed in melacocytes typically in the skin. A majority of TYR mutations deactivates tyrosinase to impair the capability of melanocytes to produce melanin life time. People with this form of albinism have white hair, light-colored eyes, and very pale skin. Some of the TYR mutations do not completely deactivate tyrosinase and melanocytes do produce some the melanin, cause OCA1B (MIM# 606952). In the current study a total of five families containing two or more affected individuals with oculocutaneous albinism (OCA) were enrolled. Clinical symptoms were recorded and pedigrees were drawn by visiting these families. Blood samples (5cc) were also collected from all affected individuals, their normal siblings and parents in EDTA containing falcon tubes. Genomic DNA was extracted using inorganic method. Linkage analysis was performed by three STR markers D11S1780, D11S1367 and D11S4175. Two families showed linkage to OCA1. Sequence analysis of exons and flanking intronic regions was performed for TYR gene. Two known missense mutations (p.Ile198Thr & p.Ser44Arg) causing oculocutaneous albinism type 1 were identified, whereas sequence analysis of normal individuals has shown no sequence change in respective codons. The current study is very important which confirms important mutations causing oculocutaneous albinism in Pakistani families.


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