Diverse deletions in the growth hormone receptor gene cause growth hormone insensitivity syndrome

Growth hormone insensitivity syndrome (GHIS; also known as Laron syndrome), is characterized by severe postnatal growth failure and normal growth hormone. The syndrome is frequently caused by point mutations in the growth hormone receptor gene (GHR). Here we report five families with GHIS and partial deletions of the GHR gene. The deletion breakpoints were sequenced and PCR-based diagnostic tests were developed. In a Cambodian family, a novel deletion removed part of exon 5 and 1.2 kb of the preceding intron. The deletion occurred by recombination within four identical nucleotides. In the mutant transcript, skipping of the truncated exon 5 leads to a frameshift and premature termination codon (PTC). A previously reported discontinuous deletion of GHR exons 3, 5, and 6 was identified in three Oriental Jewish families. An unaffected individual was heterozygous for the exon 5 and 6 deletion, but homozygously deleted for exon 3 suggesting that the exon 3 deletion is a polymorphism. The pathogenic deletion of exons 5 and 6 spans about 7.5 kb. Sequence analysis of the breakpoints revealed an imperfect junction between introns 4 and 6, with a four basepair insertion. A novel deletion of 13 nucleotides within exon 9 was identified in a Caucasian girl with GHIS who carries the I153T missense mutation on her other allele. The exon 9 deletion leads to a frameshift and PTC. The predicted protein retains the transmembrane domain and a short cytoplasmic tail. Four family members in three generations were carriers of this deletion, but only two of them were below normal for height, suggesting that this mutation by itself does not act as a dominant negative, as was reported for two other GHR mutations which lead to truncation of the intracellular domain.