POLYMORPHISM OF A VARIANT HUMAN THYROTROPIN RECEPTOR (HTSHR) GENE

Sequencing of the human thyrotropin receptor (hTSHR) gene using genomi c DNA from peripheral blood leukocytes revealed a substitution of nucl eotide 253 in the cDNA sequence. The replacement of the wild-type cyto sine-253 to adenine results in the replacement of the wild-type Pro at cc don 52 (CCC) with Thr (ACC) located in exon 1 of the TSHR. We scre ened genomic DNAs from 60 unrelated individuals for the presence of A2 53 by PCR amplification using a degenerate oligonucleotide primer that produces a Tth111 I restriction site only in the presence of A253. We found 12% having heterozygosity and all had normal free thyroxine ind ex (FT4I) and TSH levels. We have no information concerning the functi onal significance of this amino acid substitution. However, in the het erozygous state, the variant allele does not result in thyroid functio n abnormalities.