Mutation creating a new splice site in the growth hormone receptor genes of 37 Ecuadorean patients with Laron syndrome

Abstract

Laron syndrome is an autosomal recessive condition characterized by resistance to growth hormone. We sought to determine the molecular basis of this condition in an Ecuadorean population with a high incidence of affected individuals. Growth hormone receptor gene sequences from an obligate heterozygote were amplified by the polymerase chain reaction and screened for mutations using denaturing gradient gel electrophoresis. Only exon 6 revealed homo- and heteroduplexes on denaturing gradient gels. Sequencing revealed a substitution of guanine for adenine in the third position of codon 180 that did not change the amino acid encoded. Sequencing of the exon 6-exon 7 splice junction from RNA-polymerase chain reaction amplified cellular RNA of an affected individual revealed that the substitution activates a 5' splice site 24 nucleotides upstream from the normal exon 6-intron 6 boundary. Splicing in two probands' lymphoblasts occurred virtually exclusively at the abnormal 5' splice site created by the codon 180 substitution. Exon 6 sequences from 38 patients and 47 relatives were amplified and analyzed by sequencing or dot-blot hybridization with allele-specific oligonucleotides. The substitution was detected in 74 of 76 Laron syndrome patients' GH-receptor alleles. All 26 parents and 12 of 21 unaffected siblings were heterozygous for this mutation. It was absent in 61 unrelated unaffected control individuals. We conclude that the codon 180 nucleotide substitution probably causes Laron syndrome as translation of the observed, abnormally spliced growth hormone receptor transcript would lead to the synthesis of a receptor protein with an 8 amino acid deletion from the extracellular domain.

Efeito fundador da mutação E180splice no gene do receptor de hormônio de crescimento identificada em pacientes brasileiros com insensibilidade ao GH

“…Nossos pacientes compartilham o mesmo haplótipo da região variante do intron 9 dos pacientes equatorianos e dos pacientes judeus descritos (14,15). Infelizmente não tivemos acesso a informação da presença dos outros polimorfismos no gene do GHR nestes pacientes.…”

“…A mutação E180splice foi também descrita em uma comunidade andina isolada no sul do Equador descendente de espanhóis (14) e em dois pacientes de Israel com ancestrais marroquinos (15). As nossas 4 famílias compartilham o mesmo haplótipo (tipo I) da região altamente polimórfica do intron 9 dos pacientes Equatorianos e Judeus (15).…”

Novel nonsense mutation (p.Y113X) in the human growth hormone receptor gene in a Brazilian patient with Laron syndrome

“…To date, this is the most common mutation present in Brazil, as well as in the world. The mutation in codon 198, also known as E180Splice mutation, has been described in Ecuadorian patients and two Israeli patients of Moroccan descent (12,13).…”

Hormônio do crescimento ou somatotrófico: novas perspectivas na deficiência isolada de GH a partir da descrição da mutação no gene do receptor do GHRH nos indivíduos da cidade de Itabaianinha, Brasil

“…Neste modelo, há uma hipersecreção de GH com reduzidos níveis de IGF-I. Há mais de 200 indivíduos descritos com o Nanismo de Laron, e o maior agrupamento familiar com 70 indivíduos com resistência ao GH foi descrito no Equador (8).…”