Genetic regulation of pituitary gland development in human and mouse

Normal hypothalamopituitary development is closely related to that of the forebrain and is dependent upon a complex genetic cascade of transcription factors and signaling molecules that may be either intrinsic or extrinsic to the developing Rathke’s pouch. These factors dictate organ commitment, cell differentiation, and cell proliferation within the anterior pituitary. Abnormalities in these processes are associated with congenital hypopituitarism, a spectrum of disorders that includes syndromic disorders such as septo-optic dysplasia, combined pituitary hormone deficiencies, and isolated hormone deficiencies, of which the commonest is GH deficiency. The highly variable clinical phenotypes can now in part be explained due to research performed over the last 20 yr, based mainly on naturally occurring and transgenic animal models. Mutations in genes encoding both signaling molecules and transcription factors have been implicated in the etiology of hypopituitarism, with or without other syndromic features, in mice and humans. To date, mutations in known genes account for a small proportion of cases of hypopituitarism in humans. However, these mutations have led to a greater understanding of the genetic interactions that lead to normal pituitary development. This review attempts to describe the complexity of pituitary development in the rodent, with particular emphasis on those factors that, when mutated, are associated with hypopituitarism in humans

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

Background: We previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15–20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in ~ 80% of cases. Methods: We report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded. Results: No gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5–528.7, P = 1.1 × 10−4) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR = 3.70[95%CI 1.3–8.2], P = 2.1 × 10−4). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR = 19.65[95%CI 2.1–2635.4], P = 3.4 × 10−3), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR = 4.40[9%CI 2.3–8.4], P = 7.7 × 10−8). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD] = 43.3 [20.3] years) than the other patients (56.0 [17.3] years; P = 1.68 × 10−5). Conclusions: Rare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old

A novel POU1F1 mutation (p.Thr168IlefsX7) associated with an early and severe form of combined pituitary hormone deficiency: functional analysis and follow-up from infancy to adulthood

International audienceContext: POU1F1 encodes a pituitary-specific homeodomain transcription factor that is crucial for development and differentiation of anterior pituitary cell types producing GH, TSH and PRL. Although the first mutations in humans were reported in 1992, to date, less than 25 different mutations of POU1F1 have been identified worldwide.Objectives: To describe the long-term follow-up of a 22-year-old male of Israeli Arab Muslim origin, born to a consanguineous union, with congenital hypothyroidism, who presented with life-threatening hypoglycaemic episodes and severe growth retardation from infancy. To identify the molecular basis of this severe disease.Main outcome measures: Endocrine investigations, neuroimaging, sequencing of POU1F1 and assessment of the identified mutated POU1F1's ability to transactivate three specific targets (POU1F1, TSHβ and PRL).Results: Central hypothyroidism was diagnosed at the age of 2 months and GH and PRL deficiencies were documented at 9 months. MRI at 14 years revealed a hypoplastic adenohypophysis. The patient underwent spontaneous but delayed puberty. A novel disease-causing mutation (c.502insT) was identified in the homozygous state in exon 4 of POU1F1. This insertion results in a frameshift introducing an early termination codon at position 174 (p.Thr168IlefsX7), leading to a severely truncated protein lacking the entire homeodomain. This mutation abolishes POU1F1's transactivation properties on three target promoters.Conclusion: This study, which identifies a novel loss-of-function mutation in POU1F1, describes the phenotype of a rare condition in a patient followed from the first weeks of life to adulthood. The severity of the central hypothyroidism should alert clinicians to assess other pituitary axes, in particular GH and prolactin

Pitx factors are involved in basal and hormone-regulated activity of the human prolactin promoter

The pituitary-specific POU homeodomain factor Pit-1 likely interacts with other factors for cell-specific expression of prolactin. Here we identify the paired-like homeobox transcription factors Pitx1 and Pitx2 as factors functionally activating the proximal human prolactin promoter (hPRL-164luc). Using in vitro binding assays and a series of site-specific mutations of the proximal hPRL promoter, we mapped the 131 and B2 bicoid sites involved in Pitx-mediated transactivation of the hPRL-164luc construct. In somatolactotroph GH4C1 cells, basal proximal hPRL promoter activity was inhibited by a Pitx2 dominant-negative form in a dose-dependent manner, whereas binding disruptive mutations in the Pitx sites significantly reduced basal activity of the promoter. We also show that synergistic activation of hPRL-164luc by Pitx2 and Pit-1 requires the integrity of the B2 Pitx binding site, and at least one of the P1 and P2 Pit-1 response elements. In addition, mutation in the B2 Pitx site results in attenuation of the promoter's responsiveness to forskolin, thyrotropin-releasing hormone, and epidermal growth factor. Conversely, Pitx1 or Pitx2 overexpression in GH4C1 cells leads to an enhancement of the drugs stimulatory effects. Altogether, these results suggest that full responsiveness to several signaling pathways regulating the hPRL promoter requires the B2 Pitx binding site and that Pitx factors may be part of the proteic complex involved in these regulations. Finally, in situ hybridization analysis showing coexpression of the PRL and Pitx2 genes in rat and human lactotroph cells corroborates the physiological relevance of these results

Combined pituitary hormone deficiency in Australian children: clinical and genetic correlates

Objective: Mutations in the gene for the POU domain transcription factor POU1F1 (human Pit-1) have been reported in patients with GH, TSH and PRL deficiencies. PROP1 (Prophet of Pit-1) gene mutations also cause gonadotrophin deficiencies and in some cases partial ACTH deficiency. This study analyses the POU1F1 and PROP1 genes in a cohort of Australian children with combined pituitary hormone deficiency (CPHD) and correlates results with patient phenotype. Patients and Design: Genomic analysis was carried out on 33 patients with CPHD referred from centres around Australia. Clinical data were collected from medical records and referring physicans. Results: POU1F1 mutations were identified in two of four patients with a suggestive phenotype. In a female patient, novel compound heterozygous POU1F1 mutations were identified: Arg143Leu in exon 3 and Leu194Gln in exon 4. This patient presented with failure to thrive at 6 weeks of age and has deficiencies of TSH and GH. A previously described heterozygous Arg271Trp mutation in exon 6 of the POU1F1 gene was identified in a female infant who presented with growth failure and was diagnosed with TSH then GH deficiencies. No PROP1 mutations were identified; however, we describe a number of previously unreported PROP1 polymorphisms. No patients presenting with deficiencies of all anterior pituitary hormones early in life had POU1F1 or PROP1 gene mutations. Conclusions: In 33 Australian children with CPHD we have identified POU1F1 mutations in two patients and no PROP1 mutations. We speculate that in the majority of children other genes must be responsible for the CPHD phenotype.Kim McLennan, Yvette Jeske, Andrew Cotterill, David Cowley, James Penfold, Tim Jones, Neville Howard, Michael Thomsett and Catherine Choon