Background: Congenital GH deficiency (GHD) can be isolated (IGHD) or combined with other pituitary hormone deficiencies (CPHD). The identification of mutations has clinical implications for the management of patients and genetic counseling1.
Objective: To prospectively conduct a molecular-genetic analysis in genes associated with IGHD or CPHD.
Method: Forty patients with IGHD (n=8) or CPHD (n=32) were studied using target gene approach. Targeted regions (involving 26 genes associated with GHD and 57 genes associated with growth disorders without GHD) were captured using Agilent Sure Select technology. Sequencing was performed with Illumina NextSeq. Variants were analyzed considering allele frequency in the normal population and in silico prediction.
Results: We identified 31 rare allelic variants located in exons (excluding synonymous) or splice sites in 17 of 26 genes associated with GHD in 19 patients. Of these, 3 variants were considered pathogenic: one patient was compound heterozygous for a PROP1 mutation c.[109+1G>A];[301_302del] and another was heterozygous for a TGIF1 variant (c.707A>T:p.Q236L)2. Six other variants in 6 different genes (LHX3; KAL1, GLI2, GHSR, SHH and PROKR2) were considered possibly pathogenic, mainly because several in silico models predicted them to be deleterious. In the majority of cases, only one pathogenic or possibly pathogenic mutation was identified in each patient. One patient, however, is heterozygous at two loci: one variant in GLI2 and another in SHH; possibly a digenic condition. Interestingly, we identified an individual with IGHD who was compound heterozygous [c.2212C>T:p.Q738]; [c.494G>T:p.R165L] for LZTR1, a gene recently associated with Noonan syndrome (NS)3. This patients phenotype is compatible with NS diagnosis and defects in another NS related gene (SHOC2) had also been previously associated with IGHD.
Conclusion: The panel established the diagnosis of 3 patients and possibly 6 additional patients with GHD. The patients with negative results are candidates for whole exome sequencing.
References: 1. Kelberman D., et al, Genetic Regulation of Pituitary Gland Development in Human and Mouse. Endocrine Reviews, 2009, 30(7):790829. 2. A Céline, et al, Molecular screening of the TGIF gene in holoprosencephaly: identification of two novel mutations. Hum Genet, 2003, 112: 131134. 3. Yamamoto GL, et al., Rare variants in SOS2 and LZTR1 are associated with Noonan syndrome. J Med Genet, 2015, 0:19.
10 Sep 2016 - 12 Sep 2016