Analisis mutasi gen TSH B-subunit pada penderita kretin di Jawa Tengah

KUMOROWULAN, Suryati, Prof. Dr. Widya Asmara

2008 | Tesis | S2 Bioteknologi

Kretin sporadik atau hipotiroid kongenital merupakan suatu kelainan yang disebabkan kelenjar tiroid janin yang gagal memproduksi hormon tiroid secara cukup karena berbagai macam sebab. Manifestasi klinis kretin sporadik pada bayi berupa gangguan regulasi termal, gangguan gastrointestinal, gangguan neuromuskular, keterlambatan maturasi skeletal, serta keterlambatan maturasi biokimia. Pada usia lebih lanjut akan tampak gambaran kretin sporadik klasik berupa suara tangis berat dan parau, reflek tendon menurun, hernia umbilikalis, perkembangan tidak sesuai umur, hidung pesek, wajah sembab. Hipotiroid kongenital pada usia dewasa menunjukkan adanya gangguan pertumbuhan atau cebol, gangguan perkembangan psikomotor serta gangguan perkembangan intelektual (retardasi mental). Berdasar penelitian sebelumnya diketahui bahwa salah satu penyebab timbulnya hipotiroid kongenital karena adanya mutasi pada gen TSH β-subunit. Gen ini terletak pada kromosom 1 yang terdiri dari 3 exon menyandi 118 asam amino. Dari sejumlah keluarga di berbagai negara yang dipelajari terdapat jenis mutasi yang berbeda pada gen tersebut. Di Indonesia penelitian tentang gen penyebab kretin belum pernah dilakukan/dipublikasi. Tujuan penelitian ini adalah mengetahui adanya mutasi gen TSH β-subunit pada penderita kretin/hipotiroid kongenital di Indonesia khususnya di Jawa Tengah. Analisis dilakukan pada 4 keluarga penderita kretin sporadik/hipotiroid kongenital di 2 kabupaten yaitu Magelang dan Wonosobo. Seluruh anggota keluarga diperiksa secara fisik dan laboratorium. Darah baik dari individu normal maupun anggota keluarga penderita kretin diambil untuk dilakukan analisis kadar hormon TSH dan FreeT4 serta DNA darah diisolasi. Exon 2 dan exon 3 gen TSH β-subunit diamplifikasi dengan cara PCR. Untuk mengetahui ada tidaknya mutasi dideteksi dengan Restriction Fragment Length Polymorphism (RFLP) menggunakan enzim SnaBI serta dilakukan analisis Single Strand Conformation Polymorphism (SSCP). Hasil RFLP dan SSCP pada ke empat keluarga penderita kretin sporadik/hipotiroid kongenital tidak menunjukkan adanya mutasi baik pada exon 2 maupun exon 3 gen TSH β-subunit. Untuk mengetahui kemungkinan letak mutasi pada gen lain perlu dilakukan penelitian lebih lanjut.

Congenital hypothyroidism or sporadic cretinism is abnormality disorder caused by disfunction of thyroid gland to produced thyroid hormone. Clinical manifestation of congenital hypothyroidism in infant are thermal regulation disorder, gastrointestinal disorder, neuromuscular disorder, sceletal and biochemistry maturity disorder. The symptoms of congenital hypothyroidism in children include hoarse cry, umbilical hernia, oedematous of face, flat nasal bridge. In adult can cause short stature, phsycomotor disorder and mental retardation. Previous studies have shown that congenital hypothyroidism could be caused mutation in TSH β-subunit gene. The gene encoding for human TSH β- subunit is located on chromosome 1 and consists of 3 exons encoding for a protein of 118 amino acids. Different mutations in different population were reported, all located at different area of the coding region of the TSH β-subunit gene. In Indonesia, studies of gene causing by kretinism have never been reported Therefore, the objective of this research was analyze the mutation of TSH β- subunit gene of congenital hypothyroid patients in Indonesia. Four famillies with congenital hypothyroidism from Magelang and Wonosobo were analysed. The blood of affected and non affected individual from all families were collected for TSH and FreeT4 hormone analysed and DNA isolation. Exon 2 and exon 3 of the TSH β-subunit gene were amplified using PCR methods. To determine the presence of a mutation in an exon, Restriction Fragment Length Polymorphisms (RFLP) cut by SnaBI enzyme and Single Strand Conformation Polymorphism (SSCP) methods were used. The results of analyzing both by RFLP and SSCP methods showed that no mutation occur both at exon 2 and exon 3 of TSH β-subunit gene. The possibility that mutation may occur at another genes need to be further analyzed

Kata Kunci : Kretin sporadik,hipotiroid kongenital,Hormon TSH,Free T4,RFLP,Congenital hypothyroidism, TSH β-subunit gene, TSH, FreeT4, RFLP, SSCP