Haploinsufficiency of Dmxl2, encoding a synaptic protein, causes infertility associated with a loss of GnRH neurons in mouse.

Characterization of the genetic defects causing gonadotropic deficiency has made a major contribution to elucidation of the fundamental role of Kisspeptins and Neurokinin B in puberty onset and reproduction. The absence of puberty may also reveal neurodevelopmental disorders caused by molecular defects in various cellular pathways. Investigations of these neurodevelopmental disorders may provide information about the neuronal processes controlling puberty onset and reproductive capacity. We describe here a new syndrome observed in three brothers, which involves gonadotropic axis deficiency, central hypothyroidism, peripheral demyelinating sensorimotor polyneuropathy, mental retardation, and profound hypoglycemia, progressing to nonautoimmune insulin-dependent diabetes mellitus. High-throughput sequencing revealed a homozygous in-frame deletion of 15 nucleotides in DMXL2 in all three affected patients. This homozygous deletion was associated with lower DMXL2 mRNA levels in the blood lymphocytes of the patients. DMXL2 encodes the synaptic protein rabconnectin-3α, which has been identified as a putative scaffold protein for Rab3-GAP and Rab3-GEP, two regulators of the GTPase Rab3a. We found that rabconnectin-3α was expressed in exocytosis vesicles in gonadotropin-releasing hormone (GnRH) axonal extremities in the median eminence of the hypothalamus. It was also specifically expressed in cells expressing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) within the pituitary. The conditional heterozygous deletion of Dmxl2 from mouse neurons delayed puberty and resulted in very low fertility. This reproductive phenotype was associated with a lower number of GnRH neurons in the hypothalamus of adult mice. Finally, Dmxl2 knockdown in an insulin-secreting cell line showed that rabconnectin-3α controlled the constitutive and glucose-induced secretion of insulin. In conclusion, this study shows that low levels of DMXL2 expression cause a complex neurological phenotype, with abnormal glucose metabolism and gonadotropic axis deficiency due to a loss of GnRH neurons. Our findings identify rabconectin-3α as a key controller of neuronal and endocrine homeostatic processes.

Primary pigmented nodular adrenocortical disease: a case report in a 7-year-old girl.

Primary pigmented nodular adrenocortical disease (PPNAD) is a rare cause of Cushing syndrome in children, often occurring in association with Carney complex. We report a case of Cushing syndrome due to isolated non-familial PPNAD. The child presented with typical clinical characteristics, growth retardation and obesity. Liddle's test was positive but micronodular appearance was not evident on CT scan and MRI; selective venous sampling revealed higher cortisol concentrations in the right adrenal vein. The patient underwent a laparoscopic right adrenalectomy. Postoperatively, hypercortisolism signs disappeared but after the second year a slight increase in urinary cortisol was noted and the patient developed osteopenia. Although significant catch-up growth occurred postoperatively, height did not normalize over the next 2 years. When she entered puberty, treatment with a luteinizing-hormone-releasing hormone agonist was initiated and growth hormone was added. Almost 5 years later a left adrenalectomy was also performed. Thereafter, complete disease remission was observed, the patient's growth accelerated and her osteopenia reversed.

Short stature and dysmorphology associated with defects in the SHOX gene.

Since its discovery in 1997, knowledge about the SHOX gene ( Short stature HOmeoboX-containing gene) has rapidly advanced. Although originally described as causing idiopathic short stature, SHOX mutations are also responsible for growth retardation in Léri-Weill dyschondrosteosis, Langer mesomelic dysplasia and Turner syndrome. Furthermore, SHOX has a broad functional scope and leads to a variety of different morphological-skeletal stigmata associated with these syndromes. This article reviews clinical and molecular data associated SHOX gene defects. Functional ongoing studies are expected to improve our understanding of the SHOX gene as comprising part of a genetic process responsible for normal growth and bone development.

Cortisol response to adrenocorticotropin testing in non-classical congenital adrenal hyperplasia (NCCAH).

BACKGROUND: The adequacy of cortisol response in non-classical congenital adrenal hyperplasia (NCCAH) has not been fully elucidated. The aim was to evaluate cortisol response to adrenocorticotropin (ACTH) stimulation test in children and adolescents with NCCAH and heterozygotes for CYP21A2 gene mutations. METHODS: One hundred and forty-six children and adolescents, mean age 7.9 (0.7-17.5) years with clinical hyperandrogenism, were evaluated retrospectively. Thirty-one subjects had NCCAH, 30 were heterozygotes for CYP21A2 gene mutations, while 85 showed normal response to ACTH test. RESULTS: Baseline cortisol levels did not differ among NCCAH, heterozygotes, and normal responders: 15.75 (5.83-59.6) µg/dL vs. 14.67 (5.43-40.89) µg/dL vs. 14.04 (2.97-34.8) µg/dL, p=0.721. However, NCCAH patients had lower peak cortisol compared to heterozygotes and control group: 28.34 (12.25-84.40) vs. 35.22 (17.47-52.37) µg/dL vs. 34.92 (19.91-46.68) µg/dL, respectively, p=0.000. Peak cortisol was <18 µg/dL in 7/31 NCCAH patients and in one heterozygote. CONCLUSIONS: A percentage of 21.2% NCCAH patients showed inadequate cortisol response to ACTH stimulation. In these subjects, the discontinuation of treatment on completion of growth deserves consideration.

Resistance to leptin-replacement therapy in Berardinelli-Seip congenital lipodystrophy: an immunological origin.

CONTEXT: Recently, in a 4-month proof-of-concept trial, beneficial metabolic effects were reported in non-diabetic children with Berardinelli-Seip congenital lipodystrophy (BSCL); this information prompted us to hypothesize that long-term leptin-replacement therapy might improve or reverse the early complications of the disease in these patients. PATIENTS AND METHODS: A 28-month trial was implemented in eight patients. Efficacy assessment was based on a decrease in serum triglyceride concentrations, and/or a decrease in liver volume and/or an increase in insulin sensitivity of at least 30% respectively. The response was defined as follows: total (3/3 positive criteria), partial (1 or 2/3), or negative (0/3). Anti-leptin antibodies were measured with a radiobinding assay, and a neutralizing effect was assessed in primary cultures of embryonic neurons incubated with an apoptotic agent (N-methyl-D-aspartate) and the patient serum, with or without leptin. RESULTS: A negative or partial response to treatment was observed in five of eight patients even when leptin dosages were increased. A displaceable leptin binding was detectable in all patients after 2 months of treatment. At 28 months, binding was higher in the patients with a negative response than in the total responders, and it paralleled both the increase in leptin dosage and serum leptin concentrations. Co-incubation of embryonic neurons with serum from two patients with a negative response inhibited the neuroprotective effect of leptin. CONCLUSION: Under leptin therapy, patients with BSCL may develop a resistance to leptin, which could be partly of immunological origin, blunting the previously reported beneficial effects.