👤 Frédéric Di Fiore

The onset of puberty is a critical developmental milestone regulated by complex neuroendocrine networks that integrate genetic, metabolic, and environmental cues. Among the molecular systems coordinating this transition, neurotrophins-including brain-derived neurotrophic factor (BDNF), nerve growth factor, neurotrophin-3, and neurotrophin-4/5-have emerged as important modulators of hypothalamic maturation and the activation of gonadotropin-releasing hormone (GnRH) neurons. Beyond their established roles in neuronal survival and differentiation, neurotrophins contribute to hypothalamic circuit plasticity, influence GnRH neuronal activity, and participate in the integration of metabolic and environmental signals relevant to reproductive maturation. Experimental studies, primarily based on animal and cellular models, demonstrate that BDNF and its receptor play a role in normal pubertal onset, whereas disruptions in neurotrophin signaling have been implicated in central precocious puberty, delayed puberty, and hypogonadotropic hypogonadism. In humans, available evidence is more limited and derives mainly from genetic studies, circulating neurotrophin measurements, and clinical observations. This review provides an integrative synthesis of current experimental and clinical data on neurotrophin-mediated regulation of pubertal timing, highlighting both physiological mechanisms and pathological conditions. While neurotrophins represent promising modulators at the intersection of neurodevelopment, metabolism, and reproduction, further longitudinal and translational human studies are required to define their diagnostic and therapeutic potential in pediatric endocrinology. Show less

Small bowel adenocarcinoma is a rare disease. The genomic profiling tumours according to clinical characteristics and its impact on the prognosis remains unclear. A pooled analysis of clinical data, genomic profiling and MisMatch Repair (MMR) status from three databases was performed. A total of 188 tumour samples were analysed. A predisposing disease was reported in 22.3%, mainly Lynch syndrome and Crohn's disease. The tumours were localized in 80.2% and metastatic in 18.8%. The most frequent mutations were KRAS (42.0%) among them 7/79 are G12C, TP53 (40.4%), APC (19.1%), PIK3CA (18.6%), SMAD4 (12.8%) and ERBB2 (9.6%). Mutation distribution differed according to predisposing disease for TP53, ERBB2, IDH1, FGFR3, FGFR1 and KDR. KRAS and SMAD4 mutations were more frequent in metastatic tumour, whereas ERBB2 mutations were absent in metastatic tumour. For localized tumour, APC mutation was independently associated with a poor overall survival (OS) (p = 0.0254). 31.8% of localized tumours and 11.3% of metastatic tumours were dMMR (29.8% of the entire cohort). A dMMR status was associated with a better OS (HR = 0.61 [0.39-0.96], p = 0.0316). There is a different genomic profile according to the stage and predisposing disease. dMMR and APC mutation in localized tumour predict a better prognosis. Show less

We studied the impact of high prolactin titers on liver and adipocyte gene expression related to glucose and insulin homeostasis in correlation with obesity onset. To that end we used mutant female mice that selectively lack dopamine type 2 receptors (D2Rs) from pituitary lactotropes (lacDrd2KO), which have chronic high prolactin levels associated with increased body weight, marked increments in fat depots, adipocyte size, and serum lipids, and a metabolic phenotype that intensifies with age. LacDrd2KO mice of two developmental ages, 5 and 10 mo, were used. In the first time point, obesity and increased body weight are marginal, although mice are hyperprolactinemic, whereas at 10 mo there is marked adiposity with a 136% increase in gonadal fat and a 36% increase in liver weight due to lipid accumulation. LacDrd2KO mice had glucose intolerance, hyperinsulinemia, and impaired insulin response to glucose already in the early stages of obesity, but changes in liver and adipose tissue transcription factors were time and tissue dependent. In chronic hyperprolactinemic mice liver Prlr were upregulated, there was liver steatosis, altered expression of the lipogenic transcription factor Chrebp, and blunted response of Srebp-1c to refeeding at 5 mo of age, whereas no effect was observed in the glycogenesis pathway. On the other hand, in adipose tissue a marked decrease in lipogenic transcription factor expression was observed when morbid obesity was already settled. These adaptive changes underscore the role of prolactin signaling in different tissues to promote energy storage. Show less

Many proteins contain ubiquitin-binding domains or motifs (UBDs), such as the UIM (ubiquitin-interacting motif) and are referred to as ubiquitin receptors. Ubiquitin receptors themselves are frequently monoubiquitinated by a process that requires the presence of a UBD and is referred to as coupled monoubiquitination. Using a UIM-containing protein, eps15, as a model, we show here that coupled monoubiquitination strictly depends on the ability of the UIM to bind to monoubiquitin (mUb). We found that the underlying molecular mechanism is based on interaction between the UIM and a ubiquitin ligase (E3), which has itself been modified by ubiquitination. Furthermore, we demonstrate that the in vivo ubiquitination of members of the Nedd4 family of E3 ligases correlates with their ability to monoubiquitinate eps15. Thus, our results clarify the mechanism of coupled monoubiquitination and identify the ubiquitination of E3 ligases as a critical determinant in this process. Show less