DETECTION OF GROWTH-HORMONE GENE DEFECTS BY DIDEOXY FINGERPRINTING (DDF)

We carried out screening for mutations in the GH-1 gene in 29 sporadic Japanese subjects with severe Isolated Growth Hormone Deficiency (IGH D) by dideoxy fingerprinting (ddF). Three of 29 (10%) were heterozygou s for each of the following GH-1 gene mutations including: 1) an G --> A transition in the third codon of the GH-1 signal peptide of exon 1 resulting in a Threonine to Alanine substitution, 2) a G --> A transit ion in the first base of the donor splice site of IVS 3 (+1G --> A) an d 3) a G --> A transition in the 183rd codon of the GH-1 mature peptid e of exon 5 resulting in an Arginine to Histidine substitution. One of three was heterozygous for both mutations of 1) and 2). The IVS 3 (+1 G --> A) mutation has been previously reported in affected individuals from three unrelated families with IGHD type II (autosomal dominant f orm). This mutation destroys the GH IVS 3 donor splice site, causing s kipping of exon 3 and loss of the codons for amino acids 32-71 of the mature GH peptide. Our findings indicate that 1) ddF screening of geno mic DNAs provides a practical tool to detect GH gene mutations and 2) some sporadic cases of IGHD may be caused by GH gene alternations.