Molecular screening of a large cohort of Moroccan patients with congenital hypopituitarism.

BACKGROUND/OBJECTIVES: Congenital hypopituitarism is a rare disease which, for most patients, has no identified molecular cause. We aimed to document the molecular basis of growth retardation in a Moroccan cohort. DESIGN/PATIENTS: 80 index cases [54 with isolated growth hormone deficiency (IGHD), 26 with combined pituitary hormone deficiency (CPHD)] were screened for molecular defects in GH1 (including LCR-GH1), GHRHR, GHSR, GHRH, PROP1, POU1F1, HESX1, LHX3, LHX4 and SOX3. RESULTS: Five different deleterious mutations were identified in 14 patients from eight families. In the IGHD group, three genes were found to be involved: GH1, GHRHR and GHSR. In the CPHD group, PROP1 was the only mutated gene. In addition, two heterozygous variations whose deleterious effect remains to be demonstrated were identified (in GH1 and LHX4), and two polymorphisms (missense variations) were detected (in LHX3 and in GHSR). The prevalence of mutations in this Moroccan GHD cohort was 10% (8/80), 11·1% (6/54) in the IGHD group and 7·7% (2/26) in the CPHD group. CONCLUSION: This is the first molecular screening of congenital GHD in a Moroccan population and, like other studies, mutations were preferentially identified in familial cases (75%); mutations in genes such as POU1F1, HESX1, SOX3, LHX3 and LHX4 are extremely rare. The p.R73C PROP1 mutation was the most frequent mutation in CPHD; this should be the first one to screen in this population. Our results should contribute to a better diagnosis and management of this heterogeneous disease condition.

[C634R mutation of the protooncongene RET and molecular diagnosis in multiple endocrine neoplasia type 2 in a large Moroccan family]. / Mutation C634R du proto-oncogène RET et diagnostic moléculaire dans une grande famille marocaine de néoplasie endocrinienne multiple de type 2A.

Multiple endocrine neoplasia (MEN) 2A is an inherited disease characterized by the development of medullary thyroid carcinoma (MTC), pheochromocytoma and/or hyperparathyroïdism. It has been shown to be associated with germline mutations in the RET proto-oncogene. Direct DNA testing, therefore allows the identification of subjects with asymptomatic MEN 2A who can be offered prophylactic thyroidectomy and biochemical screening as preventive measures. DNA analysis of RET exon 8, 10, 13, 14, 15 and 16 was performed by direct sequencing of PCR product on automated sequencer and or PCR-digestion. In this report, we describe a MEN2A family witch initially seemed a sporadic case of MTC. We first characterized the C634R RET mutation in the index and then we identified 3 carriers who developed the disease and 3 young carriers who were apparently asymptomatic. A genetic counselling and the management of the carriers were proposed. This study confirmed that genetic testing ; in order to detect gene carriers is technically possible in Morocco. This will contribute to the definition of a national policy of this cancer control.

Unusual phenotypic features in a patient with a novel splice mutation in the GHRHR gene.

Isolated growth hormone deficiency (IGHD) may be of genetic origin. One of the few genes involved in that condition encodes the growth hormone releasing hormone receptor (GHRHR) that, through its ligand (GHRH), plays a pivotal role in the GH synthesis and secretion by the pituitary. Our objective is to describe the phenotype of two siblings born to a consanguineous union presenting with short stature (IGHD) and Magnetic Resonance Imaging (MRI) abnormalities, and to identify the molecular basis of this condition. Our main outcome measures were clinical and endocrinological investigations, MRI of the pituitary region, study of the GHRHR gene sequence and transcripts. In both patients, the severe growth retardation (-5SD) was combined with anterior pituitary hypoplasia. In addition to these classical phenotypic features for IGHD, one of the patients had a Chiari I malformation, an arachnoid cyst, and a dysmorphic anterior pituitary. A homozygous sequence variation in the consensus donor splice site of intron 1 (IVS1 + 2T > G) of the GHRHR gene was identified in both patients. Using in vitro transcription assay, we showed that this mutation results in abnormal splicing of GHRHR transcripts. In this report, which broadens the phenotype associated with GHRHR defects, we discuss the possible role of the GHRHR in the proper development of extrapituitary structures, through a mechanism that could be direct or secondary to severe GH deficiency.

Loss of constitutive activity of the growth hormone secretagogue receptor in familial short stature.

The growth hormone (GH) secretagogue receptor (GHSR) was cloned as the target of a family of synthetic molecules endowed with GH release properties. As shown recently through in vitro means, this receptor displays a constitutive activity whose clinical relevance is unknown. Although pharmacological studies have demonstrated that its endogenous ligand--ghrelin--stimulates, through the GHSR, GH secretion and appetite, the physiological importance of the GHSR-dependent pathways remains an open question that gives rise to much controversy. We report the identification of a GHSR missense mutation that segregates with short stature within 2 unrelated families. This mutation, which results in decreased cell-surface expression of the receptor, selectively impairs the constitutive activity of the GHSR, while preserving its ability to respond to ghrelin. This first description, to our knowledge, of a functionally significant GHSR mutation, which unveils the critical importance of the GHSR-associated constitutive activity, discloses an unusual pathogenic mechanism of growth failure in humans.