Three ALS Deficient Patients in a Non Consanguineous Family Presenting Four Different IGFALS Gene Variants

SCAGLIA, PAULA; KESELMAN, ANA; MARTUCCI, LUCIA; KARABATAS, LILIANA; BALLERINI, MARIA GABRIELA; DOMENE, SABINA; RODRIGUEZ AZRAK, SOL; JASPER, HECTOR; DOMENE, HORACIO

Playa del Carmen

Congreso; SOCIEDAD LATINOAMERICANA DE. ENDOCRINOLOGÍA Pediatrica; 2014

Introduction: Complete ALS deficiency (ALS-D), caused byinactivating mutations in both IGFALS gene alleles, presents severeIGF-I and IGFBP-3 deficiencies associated with moderategrowth retardation.Aim: To characterize the molecular defect in a family where theindex case and his father presented short stature and IGF-I andIGFBP-3 deficiencies.Subjects and Methods: We studied a 2.4 y old boy (A, indexcase) and his father (B), mother (C), brother (D), paternal aunt (E)and grandmother (F). IGF-I, IGFBP-3 and GH serum levels weredetermined by CLIA (Immulite, Siemmens), ALS by ELISA (Mediagnost)and Western immunoblot (WIB). In vitro ternary complexformation [TCF = (peak cpm/total cpm) x 100] was evaluated bysize exclusion chromatography (Superdex column, GE Healthcare)after incubating patients? sera with 125I-IGF-I. IGFALS gene wasPCR amplified and automatically sequenced. In silico bioinformatictools were used to predict the gene variants effects on proteinfunction. Three out of 4 IGFALS gene variants found were expressedin vitro in CHO cells and ALS expression was evaluated by WIB.Results: IGFALS sequencing in the index case (A), who presentedshort stature with normal GH secretion (GHmax: 15.3 ng/ml) and undetectable IGF-I, IGFBP-3 and ALS serum levels, revealedhe was compound heterozygous for a frameshift mutation(c.103dupG, p.E35Gfs*17) and a novel missense variant(c.1469C>G, p.S490W). His father was compound heterozygousfor the novel p.S490W variant and p.[L409F; A475V], previouslydescribed in an ALS-D consanguineous family. The patient?smother and brother, who presented normal/low levels of IGFBP-3 and ALS, were heterozygous carriers for p.E35Gfs*17 and p.S490W variants, respectively. His paternal aunt presented thesame genotype as the father while the paternal grandmother washeterozygous carrier for p.[L409F; A475V].The p.S490W, p.L409F and p.E35Gfs*17 were predicted to bepathogenic while p.A475V was predicted as benign by in silico bioinformatictools. In vitro expression in CHO cells demonstratedthat p.L409F and p.E35Gfs*17 mutants are not expressed, whilep.A475V was normally expressed and secreted.Conclusions: The finding of undiagnosed ALS-D adult subjects,compound heterozygous for IGFALS gene mutations (with eithershort or nomal height) and the appearance of heterozygous carriersin a non consanguineous family, support that these genetic variantsare present in the population and are not under a strong negativeselection pressure. Functional evaluation of these variants by in vitrocell culture expression suggests that p.E35Gfs*17 and p.L409Fare loss-of-function mutations. Remarkably, this is the first reportshowing fertility is preserved in an adult ALS-D patient.