Olga V. Fofanova

Isolated Growth Hormone Deficiency (IGHD) due to GH1 gene defects has a variable inheritance pattern: autosomal recessive, autosomal dominant, and X-linked. the autosomal dominantly inherited form, IGHD II, is mainly caused by heterozygous mutations of splicing around the exon 3/IVs3 boundary region of the GH1 gene resulting in exon 3 skipping of transcripts. We have previously reported findings on GH1 gene mutations in 28 russian patients with severe congenital IGHD (-3.22+/-1.2 height sDs at the age of 1yr); five heterozygous dominant negative splice site mutations in intron 2, intron 3, and exon 4 of the GH1 gene were identified in 32.1% of the cohort. In the present report we describe a novel 456G>A heterozygous mutation of splicing of the last base of the 3'-acceptor splice site of exon 4 within the GH1 in a 4.2-year old, extremely short (-5.32 height sDs) girl with congenital IGHD. the mutation involves a highly conserved GGGgtg sequence of the exon 4/IVs4 boundary region of the GH1 gene. the predicted effect of the 456 G>A mutation is perturbed splicing with possible skipping of exon 4 of the GH1 gene. the novel heterozygous 456 G>A mutation in exon 4 expands the spectrum of dominant negative splicing defects within the GH1 gene, responsible for congenital IGHD.

Isolated GH deficiency (IGHD) is characterized by genetic heterogeneity, both in familial and sporadic cases. To deter- mine if this statement can be applied to the Russian popula- tion, we performed screening for mutations in the GH-1 gene in children living in Russia with IGHD. Twenty-eight children from 26 families with total IGHD were studied. DNA frag- ments, covering each of four (2-5) exons of GH-1 were ampli- fied using PCR. Single-strand conformation polymorphism analysis followed by direct DNA sequencing identified five heterozygous mutations of splicing in intron 2, intron 3, and exon 4 of GH-1; three of them were not previously reported. We concentrated here on dominant-negative mutations causing IGHD type II, which were as follows: 1) A>T transversion of the second base of the 3-acceptor splice site of intron 2 (IVS2 2A>T); 2) T>C transition of the second base of the 5-donor splice site of intron 3 (IVS3 2T>C); 3) G>A transition of the first base of the 5-donor splice site of intron 3 (IVS3 1G>A). Our data indicate allelic heterogeneity of IGHD type II (IGHD II). However, all mutations in Russian IGHD II patients affect splicing, a striking difference from the mutation spectrum of other IGHD forms. The IVS2 2A>T mutation is the first iden- tified mutation in intron 2 of GH-1. The 5-donor splice site of intron 3 of GH-1 is a mutational hot spot, and the IVS3 1G>A mutation can be considered to be a common molecular defect in IGHD II in Russian patients. (J Clin Endocrinol Metab 88: 820 - 826, 2003)