Delta-Like 1 Homolog, Dlk1, is a paternally imprinted gene encoding a transmembrane protein involved in the differentiation of several cell types. After birth, Dlk1 expression decreases substantially in all tissues except endocrine glands. Dlk1 deletion in mice results in pre-natal and post-natal growth deficiency, mild obesity, facial abnormalities, and abnormal skeletal development, suggesting involvement of Dlk1 in perinatal survival, normal growth and homeostasis of fat deposition. A neuroendocrine function has also been suggested for DLK1 but never characterised. To evaluate the neuroendocrine function of DLK1, we first characterised Dlk1 expression in mouse hypothalamus and then studied post-natal variations of the hypothalamic expression. Western Blot analysis of adult mouse hypothalamus protein extracts showed that Dlk1 was expressed almost exclusively as a soluble protein produced by cleavage of the extracellular domain. Immunohistochemistry showed neuronal DLK1 expression in the suprachiasmatic (SCN), supraoptic (SON), paraventricular (PVN), arcuate (ARC), dorsomedial (DMN) and lateral hypothalamic (LH) nuclei. DLK1 was expressed in the dendrites and perikarya of arginine-vasopressin neurons in PVN, SCN and SON and in oxytocin neurons in PVN and SON. These findings suggest a role for DLK1 in the post-natal development of hypothalamic functions, most notably those regulated by the arginine-vasopressin and oxytocin systems.

PurposeCongenital hypogonadotropic hypogonadism (CHH) and split hand/foot malformation (SHFM) are two rare genetic conditions. Here we report a clinical entity comprising CHH and SHFM.MethodsWe identified patients with CHH and SHFM through international collaboration. Probands and available family members underwent phenotyping and screening for FGFR1 mutations. The impact of identified mutations was assessed by sequence- and structure-based predictions, and/or functional assays.ResultsWe identified 8 probands with CHH with (n=3, Kallmann Syndrome) or without anosmia (n=5) and SHFM, 7 of whom (88%) harbor FGFR1 mutations: one individual is homozygous for p.V429E; six individuals are heterozygous for p.G348R, p.G485R, p.Q594*, p.E670A, p.V688L, and p.L712P. All mutations were predicted to be loss-of-function by in silico analysis. Probands with FGFR1 mutations have severe GnRH deficiency (absent puberty and/or cryptorchidism and/or micropenis). SHFM in both hands and feet was only observed in the patient with the homozygous p.V429E mutation; V429 maps to the FRS2α binding domain of FGFR1, and functional studies of the p.V429E mutation demonstrated that it decreased recruitment and phosphorylation of FRS2α to FG FR 1 , thereby resulting in reduced MAPK signaling.ConclusionFGFR1 should be prioritized for genetic testing in patients with CHH and SHFM, because the likelihood of a mutation increases from 10% in the general CHH population to 88%.

Objective: Isolated congenital anosmia (ICA) is a rare phenotype defined as absent recall of any olfactory sensations since birth and the absence of any disease known to cause anosmia. Although most cases of ICA are sporadic, reports of familial cases suggest a genetic cause. ICA due to olfactory bulb agenesis and associated to hypogonadotropic hypogonadism defines Kallmann syndrome (KS), in which several gene defects have been described. In KS families, the phenotype may be restricted to ICA. We therefore hypothesized that mutations in KS genes cause ICA in patients, even in the absence of family history of reproduction disorders. Design and methods: In 25 patients with ICA and olfactory bulb agenesis, a detailed phenotype analysis was conducted and the coding sequences of KAL1, FGFR1, FGF8, PROKR2, and PROK2 were sequenced. Results: Three PROKR2 mutations previously described in KS and one new PROK2 mutation were found. Investigation of the families showed incomplete penetrance of these mutations. Conclusions: This study is the first to report genetic causes of ICA and indicates that KS genes must be screened in patients with ICA. It also confirms the considerable complexity of GNRH neuron development in humans.

Kallmann syndrome (KS) is a heterogeneous genetic disorder that associates variable gonadotropin-releasing hormone (GnRH) deficiency with anosmia and, sometimes, other non-reproductive clinical features. X-linked recessive, as well as autosomal recessive and dominant modes of transmission have been described. The first KS-related gene to be described (KAL1) was in the X-linked form. The second gene (KAL2) was initially unexpected, as it was known to encode the fibroblast growth receptor 1 (FGFR1). Its consideration as a candidate gene arose as a result of cases with contiguous gene syndrome and, initially, mutations were mostly described in familial cases with autosomal dominant transmission of KS. Since its initial discovery, numerous mutations of FGFR1 have been described in several functional domains of the receptor. Genotype-phenotype correlations have shown that some clinical features associated with KS, such as loss of nasal cartilage, hearing impairment, and anomalies of the limbs seem to be mainly associated with KAL2 mutations. The role of FGFR1 in the normal development of the olfactory bulb explains the association of anosmia with GnRH deficiency in FGFR1-mutated patients. Phenotype analysis indicates that FGFR1 is involved in normal migration of GnRH fetal neurons, but this is clearly not the whole story as a substantial proportion of KAL2-mutated individuals have normosmic GnRH deficiency. Finally, recent additional observations, notably using animal models, but also the description of human mutations in a specific ligand of FGFR1, FGF8, are beginning to shed light on the pathogenesis of GnRH deficiency in general, not just KS.

Objective To compare symptoms and sleep characteristics in patients diagnosed with narcolepsy‐cataplexy (NC) before and after the age of 18 years. Methods De novo patients with NC diagnosis completed a standardized questionnaire and interview, followed by a sleep study. The clinical and sleep measures were compared between patients diagnosed before (46 children, median age: 12 year old) and after (46 adults, median age: 28.5 year old) 18 years of age. Results The frequency of obesity (54% vs 17%), night eating (29% vs 7%), parasomnia (89% vs 43%), sleep talking (80% vs 34%), and sleep drunkenness (69% vs 24%) were higher in children than in adults, the frequency of sleep paralysis was lower (20% vs 55%) but the frequency of cataplexy and the severity of sleepiness were not different. Children scored higher than adults at the attention‐deficit/hyperactivity disorder (ADHD) scale. Depressive feelings affected not differently children (24%) and adults (32%). However, adults had lower quality of life than children. There was no difference between groups for insomnia and fatigue scores. Quality of life was essentially impacted by depressive feelings in both children and adults. Obstructive apnea‐hypopnea index (OAHI) was lower in children with higher mean and minimal oxygen saturation than in adults. No between‐group differences were found at the multiple sleep latency test. The body mass index (z‐score) was correlated with OAHI (r = .32). Conclusion At time of NC diagnosis, children have more frequent obesity, night eating, parasomnia, sleep talking, drunkenness, and ADHD symptoms than adults, even if sleepiness and cataplexy do not differ. These differences should be considered to ensure a prompt diagnosis.

Narcolepsy type 1 children had a higher CSF HA level together with a lower t-MeHA level leading to a significant decrease in the t-MeHA/HA ratios. These results suggest a decreased HA turnover and an impairment of histaminergic neurotransmission in narcoleptic children and support the use of a histaminergic therapy in the treatment against narcolepsy.

Puberty is a complex maturation process that begins during fetal life and persists until the acquisition of reproduction function. The fundamental event that activates puberty occurs in the hypothalamus. A complex neuron network stimulates GnRH secretion, which stimulates pituitary gonadotropin secretion and then gonadal steroid secretion. Pubertal delay is defined as the presentation of clinical signs of puberty 2-2.5 SD later than in the normal population. Three major groups of etiopathogeneses are described: (1) hypogonadotropic hypogonadism, (2) hypergonadotropic hypogonadism, and (3) constitutional delay of puberty (CDP) - the most common cause of delayed puberty in boys. The differential diagnosis between CDP and isolated hypogonadotropic hypogonadism remains difficult. Mechanisms of pubertal timing are now better understood and genetic or epigenetic causes can explain some pubertal delays. However, there are still unexplained mechanisms. Treatment of delayed puberty is necessary to ensure full pubertal development for the adolescent and in case of hypogonadism, to restore fertility. Finally, precocious diagnosis of hypogonadism is primordial but can be difficult during childhood and in cases of partial hypogonadism. The study of genetic pubertal diseases or of different animal models could help to discover new diagnostic or therapeutic tools.

Background and objectivesIdentifying virilisation of the genitalia in female newborns early during the neonatal period is important to diagnose pathologies. However, there is no clear threshold for clitoromegaly or for the anogenital ratio. The objective of this study was to define reference values for the external genitalia of full-term and pre-term female neonates.DesignThis was a prospective study of all females born in the study centre between May 2014 and July 2016. Clitoral length and anogenital ratio were measured in 619 newborns with a gestational age of 24+2 to 41+3 weeks during their first 3 days of life. Associations between the values at day 3 and gestational age, birth weight and other newborn characteristics were examined by linear regression.ResultsThe mean clitoral length at day 3 of life was 3.69±1.53 mm (n=551; 95th percentile, 6.5 mm; maximum, 8 mm), and the mean anogenital ratio was 0.42±0.09 (95th percentile, 0.58). There was no significant variation with gestational age or birth weight, and no significant difference between the results at day 0 and day 3.ConclusionThese results suggest that clitoromegaly can be defined as a clitoral length >6.5 mm. Values ≥8 mm should prompt further investigations. An anogenital ratio >0.6 should be considered a sign of virilisation. Since clitoral size does not vary with gestational age or birth weight, clitoromegaly should not be attributed to prematurity.