ANALISIS SEKUEN EKSON 5 GEN MATP PADA PENDERITA OCULOCUTANEOUS ALBINISM (OCA) DI YOGYAKARTA

ETI ARINASTITI, Dr. Niken Satuti Nur Handayani, M.Sc.

2011 | Tesis | S2 Bioteknologi

Albinisme adalah kelainan genetik turunan yang disebabkan gangguan pembentukan melanin atau pigmen pada kulit, rambut, dan mata. Berdasarkan ciri klinisnya, albinisme dibedakan menjadi 2 tipe yaitu Ocular Albinism (OA) dan Oculocutaneous Albinism (OCA). Salah satu tipe OCA yakni OCA4 yang disebabkan mutasi pada gen MATP. Berdasarkan analisis fenotip pada penelitian sebelumnya, 2 penderita OCA di DIY digolongkan sebagai OCA2 atau OCA4. Berdasarkan metode SSCP yang telah dilakukan, diduga ditemukan mutasi antara lain pada ekson 3 dan 5 gen MATP. Namun demikian belum diketahui letak dan tipe mutasi yang terjadi pada gen tersebut. Penelitian ini bertujuan untuk mengetahui tipe dan letak mutasi pada ekson 3 dan 5 gen MATP, mengkaji kaitan antara letak mutasi dengan perubahan asam amino, serta mengkaji kaitan perubahan asam amino dengan struktur sekunder protein MATP. DNA diisolasi dari sampel darah penderita E6 dan E7 pada keluarga di DIY. Fragmen DNA ekson 3 gen MATP individu E6 dan ekson 5 gen MATP individu E7 diamplifikasi menggunakan metode PCR. Hasil amplifikasi ekson 3 dan ekson 5 masing-masing digunakan sebagai template untuk sekuensing di 1st Base Laboratory. Analisis prediksi struktur sekunder protein MATP dilakukan menggunakan program Psipred. Hasil sekuensing menunjukkan bahwa gen MATP ekson 3 individu E6 tidak ditemukan adanya mutasi. Sementara itu, gen MATP ekson 5 individu E7 menunjukkan adanya mutasi. Tipe dan letak mutasi pada ekson 5 gen MATP individu E7 berupa transisi Guanin menjadi Adenin pada basa nomor 1045 (c.1045G>A) serta transversi Sitosin menjadi Guanin pada basa nomor 1122 (c.1122C>G). Mutasi c.1045G>A menyebabkan perubahan asam amino ke-349 yakni glisin (kodon GGG) menjadi arginin (kodon AGG), sedangkan mutasi c.1122C>G menyebabkan perubahan asam amino ke-374 yakni fenilalanin (kodon TTC) menjadi leusin (kodon TTG). Kedua mutasi tersebut merupakan mutasi missense (mutasi salah arti). Analisis menggunakan program Psipred menunjukkan adanya perubahan struktur sekunder protein MATP mutan

Albinism is a genetic disorder caused by mutation of the gen encode melanin (the skin, hair, and eye pigments). Clinically, albinism is divided into 2 types, those are Ocular Albinism (OA) and Oculocutaneous Albinism (OCA). One of the OCA types is OCA4, caused by MATP gene mutation. Based on phenotype analysis on recently research, 2 samples (E6 and E7) in Daerah Istimewa Yogyakarta (DIY) are categorized as OCA2 or OCA4. Based on SSCP result of recent study, it has been predicted that there are mutations. Those mutations are on the exon 3 and exon 5 of MATP gene, however there was no further results about position and the type of mutation. Therefore, sequence analysis especially on exon 3 and exon 5 MATP gene are needed to determine the OCA type. The aim of this research is to determine the type and mutation position in exon 3 and exon 5 MATP gene, to study the relationship between mutatio n position with alteration of amino acid in MATP protein, and to know the relationship between alteration of amino acid with the secondary structure of MATP protein. DNA was isolated from 2 blood samples of 2 individuals with albinism (E6 and E7). PCR amplification was performed to produce the exon 3 MATP gene of E6 individual and exon 5 MATP gene of E7 individual fragment. Then, the PCR product was used as template for sequencing in the 1st Base Laboratory. Secondary structure of MATP protein was predicted by Psipred analysis. Sequencing results revealed that mutation in exon 3 MATP gene of E6 individual was not found, while mutation exon 5 MATP gene of E7 individual was found. The mutation type and position on exon 5 MATP gene of E7 individual were substitution of Guanin to Adenin on base number 1045 (c.1045G>A) and transvertion of Cytosin to Guanin on base number 1122 (c.1122C>G). The c.1045G>A mutation caused the alteration of amino acid number 349 (glysin to arginine) and c.1122C>G mutation caused the alteration of amino acid number 374 (phenylalanine to leucine). These two mutations are called by missense mutations. Based on Psipred analysis revealed the alteration of secondary structure of MATP protein mutant.

Kata Kunci : Albinisme, OCA4, MATP, ekson 5, substitusi, missense, struktur sekunder