POU1F1 mutations in combined pituitary hormone deficiency: differing spectrum of mutations in a Western-Indian cohort and systematic analysis of world literature

Central precocious puberty in Prader-Willi syndrome: a narrative review

Prader-Willi syndrome (PWS, OMIM176270) is a rare genetic disorder with recognizable dysmorphic features and multisystemic consequences such as endocrine, neurocognitive and metabolic ones. Although most patients with Prader-Willi syndrome exhibit hypogonadotropic hypogonadism, there is variability regarding sexual maturation, with precocious puberty occurring in rare cases. Our aim is to elaborate a thorough review of Prader-Willi patients with central precocious puberty, in order to raise awareness of such cases and to enhance our knowledge regarding the diagnosis and prompt treatment of this particular PWS patients.

POU1F1/Pou1f1 c.143-83A > G Variant Disrupts the Branch Site in Pre-mRNA and Leads to Dwarfism

POU Class 1 Homeobox1 (POU1F1/Pou1f1) is a well-established pituitary-specific transcription factor, and causes, when mutated, combined pituitary hormone deficiency in humans and mice. POU1F1/Pou1f1 has 2 isoforms: the alpha and beta isoforms. Recently, pathogenic variants in the unique coding region of the beta isoform (beta domain) and the intron near the exon-intron boundary for the beta domain were reported, although their functional consequences remain obscure. In this study, we generated mice carrying the Pou1f1 c.143-83A>G substitution that recapitulates the human intronic variant near the exon-intron boundary for the beta domain. Homozygous mice showed postnatal growth failure, with an average body weight that was 35% of wild-type littermates at 12 weeks, which was accompanied by anterior pituitary hypoplasia and deficiency of circulating insulin-like growth factor 1 and thyroxine. The results of RNA-seq analysis of the pituitary gland were consistent with reduction of somatotrophs, and this was confirmed immunohistochemically. Reverse transcription polymerase chain reaction of pituitary Pou1f1 mRNA showed abnormal splicing in homozygous mice, with a decrease in the alpha isoform, an increase in the beta isoform, and the emergence of the exon-skipped transcript. We further characterized artificial variants in or near the beta domain, which were candidate positions of the branch site in pre-mRNA, using cultured cell-basis analysis and found that only c.143-83A>G produced transcripts similar to the mice model. Our report is the first to show that the c.143-83A>G variant leads to splicing disruption and causes morphological and functional abnormalities in the pituitary gland. Furthermore, our mice will contribute understanding the role of POU1F1/Pou1f1 transcripts in pituitary development.

Pituitary stalk interruption syndrome: phenotype, predictors, and pathophysiology of perinatal events

PURPOSE

There is limited data regarding Pituitary Stalk Interruption Syndrome (PSIS) from India. Moreover, the pathophysiological link between perinatal events and PSIS is unclear. We aim to elucidate the predictors of PSIS among patients with growth hormone deficiency (GHD) and perinatal events in PSIS by comparing cohorts of PSIS and genetically proven GHD without PSIS.

METHODS

Among 179 GHD patients, 56 PSIS and 70 genetically positive GHD (52-GHRHR, 15-POU1F1, and 3-PROP1) patients were included. Perinatal events, clinical anomalies, pituitary hormone deficiency, and imaging findings were recorded. We compared PSIS-isolated GHD (PSIS-IGHD) subgroup with GHRHR-IGHD and PSIS-combined pituitary hormone deficiency (PSIS-CPHD) subgroup with POU1F1/PROP1-CPHD.

RESULTS

PSIS patients (45 males, median age: 12.5 years) most commonly presented with short stature. At last follow-up (median age: 17.35 years), gonadal (during pubertal-age), thyroid and cortisol axes were affected in 81.6%, 62.5%, and 62.5%. 10/13 (77%) of PSIS children with initial IGHD diagnosis manifested hypogonadism during pubertal age. Male predominance, sporadic presentation, and clinical anomalies were significantly higher in both PSIS subgroups than in the respective genetic subgroups. Breech presentation was higher in PSIS-CPHD than POU1F1/PROP1-CPHD (44.4% vs 5.5%, p = 0.004). Neonatal hypoglycemia (22% vs. 0%, p = 0.05) and jaundice (42 vs. 5%, p = 0.004) were higher in PSIS-CPHD than PSIS-IGHD.

CONCLUSION

Later age at presentation and frequent hypogonadism were observed in our PSIS cohort. Male sex, sporadic presentation, clinical anomalies, and breech presentation predicted PSIS at presentation. Breech presentation in PSIS is likely due to stalk interruption rather than hormonal deficiency.

High-throughput splicing assays identify missense and silent splice-disruptive POU1F1 variants underlying pituitary hormone deficiency

Pituitary hormone deficiency occurs in ∼1:4,000 live births. Approximately 3% of the cases are due to mutations in the alpha isoform of POU1F1, a pituitary-specific transcriptional activator. We found four separate heterozygous missense variants in unrelated individuals with hypopituitarism that were predicted to affect a minor isoform, POU1F1 beta, which can act as a transcriptional repressor. These variants retain repressor activity, but they shift splicing to favor the expression of the beta isoform, resulting in dominant-negative loss of function. Using a high-throughput splicing reporter assay, we tested 1,070 single-nucleotide variants in POU1F1. We identified 96 splice-disruptive variants, including 14 synonymous variants. In separate cohorts, we found two additional synonymous variants nominated by this screen that co-segregate with hypopituitarism. This study underlines the importance of evaluating the impact of variants on splicing and provides a catalog for interpretation of variants of unknown significance in POU1F1.