ResearchPad - hypothalamic-pituitary-development-and-function Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[SAT-286 TSH Synthesis and Secretion Are Unperturbed in Male IRS4 Knockout Mice]]> It was recently reported that mutations in the insulin receptor substrate 4 (IRS4) gene cause a novel form of X-linked congenital central hypothyroidism (OMIM 300904). To date, four different mutations, three frameshift and one nonsense, have been reported, with two affected male patients showing decreased basal, pulsatile, and total thyroid-stimulation hormone (TSH) secretion (PMID 30061370).

Members of the IRS family canonically act as scaffold proteins between tyrosine kinase receptors and their downstream effectors. IRS4/Irs4 expression is enriched in the pituitary; however, its role in the hypothalamic-pituitary-thyroid (HPT) axis has not been studied in detail.

We generated novel whole-body Irs4-knockout mouse lines using CRISPR-Cas9. A specific guide RNA was used to target the Cas9 enzyme to the 5’ end of the single exon Irs4 gene. A two-nucleotide deletion was introduced into Irs4, resulting in a frameshift and premature stop codon. We hypothesized that like IRS4 deficient patients, these mice would exhibit central hypothyroidism. Given that Irs4 is X-linked, we focused our initial characterization on males.

Under normal laboratory conditions, Irs4 knockout mice do not exhibit differences in pituitary expression of Tshb, which encodes one of the subunits of the TSH heterodimer. Expression of the gene encoding the thyrotropin-releasing hormone (TRH) receptor, Trhr1, is also unperturbed in these knockout mice. Additionally, there are no differences in their serum thyroid hormones, T3 (triiodothyronine) and T4 (thyroxine). When Irs4 knockout males were placed on a low-iodine diet supplemented with propylthiouracil (PTU) for 3 weeks and rendered hypothyroid, their serum TSH increased similarly to wild-type males. Overall, Irs4 knockout males do not exhibit central hypothyroidism or phenocopy IRS4 deficient patients. Compensation by another IRS protein may explain euthyroidism in these mice.

<![CDATA[SAT-281 Chronic, Excess Growth Hormone Action Alters the Development and Aging of the Microbial Community in the Mouse Gut]]> Emerging evidence proposes that the gut microbiome has an vital role in host growth, metabolism and endocrinology. That is, gut microbes impact growth by potentially altering the growth hormone (GH)/insulin-like growth factor-1 axis. Our previous research has also shown that GH - in states of absence and excess - is associated with altered gut microbial composition, maturity and predictive metabolic function in mice. Moreover, both GH and the gut microbiome are implicated in development and aging. Yet, it is unknown how GH impacts the longitudinal microbiome. This study thus aimed to characterize the longitudinal changes in the gut microbial profile of bovine GH transgenic mice (a model of chronic, excess GH action and accelerated aging). Microbial composition was quantified from fecal pellets of the same bGH and control mice at 3, 6 and 12 months of age through 16S rRNA gene sequencing and QIIME 2. Additional bioinformatic analyses assessed the unique signature and predictive metabolic function of the microbiome. The bGH mice had a distinct microbial profile compared to controls longitudinally. At 3 months, bGH mice had increased Firmicutes and Actinobacteria, decreased Bacteroidetes, Proteobacteria and Campylobacterota, and a significant reduction in microbial richness and evenness. By 6 months, all of the aforesaid phyla were increased with the exception of Firmicutes. By 12 months, bGH mice exhibited dysbiosis with increased Firmicutes and Proteobacteria and reduced Bacteroidetes, microbial richness and evenness. Moreover, abundance in Firmicutes, Bacteroidetes and Campylobacterota were significantly explained by the combined effect of genotype and age (p = 0.006, 0.005 and 0.02, respectively). Across all timepoints, bGH mice had a significantly different microbiome compared to controls (p = 0.002), and the development of microbial richness and evenness were also significantly different in bGH mice (p = 0.034 and 0.023). Bacterial genera Lactobacillus, Ruminococcaceae and Lachnospiraceae were identified as a unique candidates in bGH mice across all timepoints. Likewise, metabolic pathways involved in biosynthesis of heme b, menaquinol, acetate and butyrate differentiated the longitudinal bGH microbiome. Collectively, these results show that chronic, excess GH impacts the development and aging of the gut microbiome. Notably, several of the stated bacterial genera and metabolic pathways were associated with GH in our previous study, suggesting that GH may influence the longitudinal presence of certain gut microbes and metabolic functions. Additional studies will be performed to further explore the GH-associated gut microbiome and its impact on host health. Research was partially funded by the John J. Kopchick MCB/TBS Fellowship, a fellowship from the Osteopathic Heritage Foundation and the MMPC at UC, Davis (NIH grant U240DK092993).

<![CDATA[OR16-04 OTX2 Mutations in Congenital Hypopituitarism Patients]]> The transcription factor OTX2 is implicated in pituitary, ocular and craniofacial development. Mutations have been described in patients with variable congenital hypopituitarism (CH) ranging from isolated growth hormone deficiency (IGHD) to combined pituitary hormone deficiency (CPHD) with/without an ectopic posterior pituitary (EPP).We aimed (i) to establish the contribution of OTX2 mutations in the etiology of CH in a sub-cohort of patients and to study their functional consequences and (ii) establish a detailed human OTX2 expression profile in a hypothalamo-pituitary (HP) context. We screened 127 patients from national (n=103) and international centers (n=24) on the septo-optic dysplasia (SOD) spectrum with variable eye abnormalities. Eye abnormalities included micro/anophthalmia, retinal dystrophy and/or coloboma in 29 of these patients, with the rest having optic nerve hypoplasia (ONH). An EPP was reported on MRI in 35 patients. The cohort previously tested negative for mutations in HESX1, SOX2, SOX3, PROKR2 and GH1. Transactivation assays involved a dual-luciferase reporter in murine hypothalamic GT1-7 neurons transiently transfected with OTX2 constructs. In situ hybridization was performed to analyze human brain OTX2 expression during embryogenesis. Seven heterozygous OTX2 changes were identified: two chromosomal deletions spanning OTX2 in patients with micro/anophthalmia, GHD and an EPP, with one patient having cerebellar hypoplasia. Three missense substitutions resulting in truncated proteins: (i) the previously reported p.S138* and (ii) p.C170*, in two patients with retinal dystrophy, EPP and IGHD respectively, and (iii) the novel p.E79* in a patient with micro/anophthalmia, EPP and CPHD. A novel insertion-deletion resulting in a truncated protein p.S167* in a patient with microphthalmia, GHD, ONH, EPP and an enlarged abnormal pituitary, and a novel deletion resulting in a frameshift p.Val139Aspfs*39 in a patient with microcephaly, microphthalmia, ONH and an EPP were also identified. The human OTX2 variants caused a significant reduction in transactivation compared to wild type. Our gene expression data identified human OTX2 transcripts in the posterior pituitary, retina, ear, thalamus, choroid plexus, and in the hypothalamus during embryogenesis, but not in RP. To conclude, we identified OTX2 variants in 7 unrelated CH patients with eye abnormalities including 3 with retinal dystrophy and one with a cerebellar abnormality. As OTX2 is involved at multiple levels during HP development, these patients should be monitored for evolving endocrinopathies. Human OTX2 is expressed in the posterior pituitary, the retina and the ear at CS19 and 20 (between 6-7 weeks gestation), and in areas of the hindbrain at CS23, but not in RP at any stage analyzed in this study. The endocrine phenotypes in patients with OTX2 mutations are most likely of hypothalamic origin.

<![CDATA[SAT-295 An Extremely Rare Novel Missense Variant C.912G≫A; P.M304I in SOX3 Gene Is Responsible for X-Linked GH Deficiency in a Brazilian Boy Without Mental Retardation]]> SOX3 (SRY-related HMG-box gene 3), located in the X chromosome, spans only one exon and is expressed in the infundibulum, diencephalon and hypothalamus. Alterations in SOX3, mainly deletions or insertions in the polyalanine tract, were associated with mental retardation, isolated GH deficiency (IGHD) or combined pituitary hormone deficiencies (CPHD). Missense variants are rare and only two were reported. Our aim was to find a molecular cause in patients with pituitary hormone deficiency and determine genotype-phenotype correlation. Twenty-eight patients (15F:13M) 24 CPHD:4 IGHD were selected for the study. Whole blood DNA was extracted using the Salting Out method. Library preparation was performed following Agilent’s SureSelectXT customized gene panel protocol containing 654 genes known to cause endocrine diseases. Illumina NextSeq 500 platform was used for sequencing at SELA. Alignment to genome reference hg19 was performed using BWA-MEM. Variants were called with FreeBayes and annotated by Annovar. Allele frequency ≤1% for exonic regions was considered in 1000 Genomes, gnomAD, ABraOM and SELA populational databases for variant filtering. Family segregation was done using Sanger sequencing. RNA and protein analysis were performed using mfold and YASARA, respectively. Protein models were made by I-Tasser. SOX3 missense variant (c.912G>A/p.M304I) was found in one male patient, without mental retardation, diagnosed with IGHD at the age of 7 years. After GH replacement, he reached final height at the age of 18 within family target height. Pituitary image showed an ectopic posterior pituitary, hypoplastic anterior pituitary and thin pituitary stalk. SOX3 (c.912G>A/p.M304I) variant in hemizygous state was absent in populational data banks. In silico prediction algorithms SIFT, PolyPhen, and Mutation Assessor were predicted as damaging. Family segregation showed normal mother and sister carriers of the variant, while father, brother and uncle (from mother’s side), all phenotypically normal, did not harbor the variant. RNA In silico analysis pointed that the variant causes mRNA structure change. Protein stability dropped from 677.46 kcal/mol in wild type to 666.69 kcal/mol in p.M304I, making it less stable. Protein Interaction analysis with DNA binding motif (PDB 2LE4) required two times less energy in mutant (376.19 kcal/mol) than wild type protein (646.77 kcal/mol), leading to a less stable interaction. We conclude that one among 28 patients presented a rare novel variant in SOX3 associated to IGHD in a patient without mental retardation and compatible with an X-linked inheritance pattern.

<![CDATA[SAT-291 SIX3 Is Essential for Hypothalamic and Pituitary Development]]> The genetic basis for congenital hypopituitarism and related disorders is beginning to emerge, and over causal 30 genes have been identified, including six in the SHH signaling pathway. Mutations in some of these genes can also cause holoprosencephaly (HPE) or septo-optic dysplasia. SIX3 is a homeodomain protein expressed in the developing brain, pituitary gland, and eye. It activates SHH signaling and represses BMP signaling. Heterozygous mutations in SIX3 cause variable HPE in humans and mice. We identified a rare, heterozygous variant in SIX3 in two children with neonatal GH and TSH deficiency and stalk interruption, p.P74R. Using transient transfection in 3T3 cells, we demonstrated that the variant reduced the ability of SIX3 to transactivate the SHH enhancer and promoter of FOXG1, suggesting that the variant could be deleterious. To understand the role of SIX3 in hypothalamic and pituitary development we used Nkx2.1-cre and Prop1-cre to delete Six3 in mice. The Nkx2.1-cre, Six3flox/flox embryos had no evidence of infundibulum evagination or expression of Fgf10 or Tcf7l2 at e11.5. The oral ectoderm invaginated in mutants, but no definitive Rathke’s pouch formed. There was no evidence of Lhx3 expression and only trace amounts of Pitx1, indicating that pituitary induction failed due to the lack of Six3 in the developing hypothalamus. Similarly, disruption of Six3 expression in Rathke’s pouch using Prop1-cre ablated pituitary development. Together, these data reveal essential roles of Six3 in both the neural and oral ectoderm for hypothalamic and pituitary development, respectively. Heterozygous loss of function variants in SIX3 could be a contributor to multiple pituitary hormone deficiencies in children, especially if there are associated craniofacial abnormalities.

<![CDATA[SAT-290 Food Restriction Effects on the Hypothalamus-Pituitary-Gonadal Axis]]> It is well known that nutritional status affects the reproduction, since an adequate amount of energy is necessary for puberty onset and fertility. However, the neural mechanisms by which energy homeostasis affects reproduction is not completely elucidated. To determine if acute or chronic food restriction (FR) are able to modulate the estrous cycle, adult female mice were used in the experiments. The estrous cycle was evaluated by daily observation of vaginal smear. To determine the effects of an acute FR protocol on estrous cycle, females were individualized and kept on ad libitum diet (control, n=17) or fasted for 24 hours (n= 21). A subgroup of animals was euthanized shortly after the 24-hours test to collect hypothalamus and determinate Kiss1 mRNA levels, while another group of mice were regrouped and fed ad libitum. To determine the effects of a chronic FR protocol on estrous cycle, control mice were individualized and maintained with 100% of daily food content (average of 5 g per day, n = 6), or submitted to 60% of FR (n= 12). Animals were fed ad libitum after test. As expected, mice fasted for 24-hours exhibited a significant weight loss (control: 21.7 g ± 0.5 vs 21.6 ± 0.5 g; fasted: 22.7g ± 0.5 vs 18.7g ± 0.4, P=0.0001). This effect was followed by a significant reduction of hypothalamic Kiss1 mRNA expression (control: 1.0 ± 0.2; fasted: 0.3 ± 0.05, P=0.04, n=4/4 per group). Surprisingly, even under lower Kiss1 mRNA levels, 24-hours fasting induced no changes on estrous cycle. On the other hand, chronic FR induced a gradual weight loss (body weight at the 5th day of FR, control: 21.5g ± 0.2; FR: 17.3g ± 0.7, P=0.0002). The chronic FR was follow by the disruption of estrous cyclicity. While control mice exhibited a regular pattern of cyclicity during the period of evaluation, only leukocytes were identified in the vaginal smear of mice submitted to 60% of FR, even though they had a normal cycling pattern before the test. Therefore, by comparing 30 days of estrous cycle evaluation, including the period before chronic FR, while control mice exhibited cornified cells in the vaginal smear 58.5 ± 4.9% of days, female mice submitted to FR exhibited cornified cells in 38.3 ± 3.8% of days (P= 0.0068). Approximately 3-4 days after the end of the chronic FR females returned to exhibit estrous cyclicity, however the length of the estrous cycle was prolonged compared to control group. Our data suggest that chronic nutritional status variations are required to disrupt the hypothalamus-pituitary-gonadal axis and therefore the estrous cyclicity.

<![CDATA[SAT-285 TSH/TSHR Signaling Deficiency Impairs Spatial Learning and Memory]]> Background: Subclinical hyperthyroidism is associated with cognitive impairment, but the mechanism has remained unclear. As subclinical hyperthyroidism is characterized by significantly decreased TSH levels, this study aimed to investigate whether TSH regulates cognitive function. Methods: The correlation between TSH and cognitive impairment was investigated in a cross-sectional population study. The role of TSH/TSH receptor (TSHR) signaling in spatial learning and memory was further examined by behavior tests in Tshr-/- mice. Dendritic spine, synaptic density and structure of hippocampal CA1 pyramidal neurons were detected by Golgi’s method and electron microscopy. The mRNA and protein expression levels of learning and memory-related genes were assessed by RNA sequencing, real-time PCR, immunoblotting and immunofluorescence approaches. Results: Serum TSH level correlated negatively with cognitive impairment in the current population. Consistently, Tshr deletion in mice led to significantly compromised performance in hippocampus-dependent tasks, reduced dendritic spine density and excitatory synaptic density as well as altered synaptic structure in CA1 subfield of the hippocampus. Furthermore, the mRNA levels of learning and memory-related genes were altered, and protein levels of CREB-regulated genes were downregulated in the hippocampus of Tshr-/- mice. Conclusions: These findings reveal that TSH/TSHR signaling ablation impairs spatial learning and memory, indicating a decline in TSH level might contribute to the increased prevalence of cognitive impairment in subclinical hyperthyroidism patients.

<![CDATA[OR16-05 Single-Cell Sequencing Identifies Novel Regulators of Thyrotrope Populations and POU1F1-Independent Thyroid-Stimulating Hormone Expression]]> <![CDATA[SAT-LB56 Undernutrition Reduces Transcript Abundance of Kisspeptin and Neurokinin B in Young Male Sheep]]> <![CDATA[SAT-LB59 Functional MRI Study: Weight Loss Induced Changes in Taste Receipt-Induced Activation in the Striatum and Hypothalamus]]> <![CDATA[SAT-284 Musashi Exerts Translational Control Within Anterior Pituitary Cells of the POU1F1 Lineage]]>


The activation of transcription factor

at embryonic day 13 gives rise to the pituitary populations of somatotropes, lactotropes, and thyrotropes and these populations maintain expression of

throughout life. The Musashi family of RNA regulatory proteins is known to regulate stem cell fate by repressing translation of target mRNAs needed for differentiation. Previously our lab has shown that female

-null somatotropes have reduced POU1F1 protein levels but do not have changes in

mRNA expression. Stimulation with leptin increased the POU1F1 protein levels 3-fold, but did not change

mRNA suggesting a post-transcriptional mechanism for leptin’s regulation of

. An

analysis indicated the presence a number of potential regulatory elements (MBEs) within the

mRNA 3’ UTR, including 8 consensus Musashi binding elements. Interestingly, we found

mRNA and protein levels were increased in

-null somatotropes. This suggested that leptin regulates the expression of

in somatotrope populations and may be a candidate translational regulator of the

mRNA. We verified that MSI binds directly to the


and exerts translational repression (using reporter mRNA assays in transfected cell populations). Single cell RNA sequencing of pituitary cells from control male and female mice indicates that


mRNAs are co-expressed in somatotropes, lactotropes as well as thyrotropes. Immunocytochemical analyses confirmed that Musashi protein is present in mixed and purified somatotrope populations. Furthermore, immunoprecipitation with Musashi1 antibody showed a 5-fold enrichment of

mRNA in control female mouse pituitaries. These findings point to a critical

role for Musashi-mediated mRNA translational regulation within the Pou1f1 lineage and specifically in the control of somatotrope maturation and response to metabolic cues.

<![CDATA[SAT-289 Evidence That Combined Pituitary Hormone Deficiency Frequently Has a Digenic/Oligogenic Etiology]]> 10, confirmed by examining BAM files, population frequency <1%, <2 homozygous subjects in gnomAD, and pathogenic prediction by at least 2 out of 3 prediction algorithms (SIFT, MutationTaster, PolyPhen2)) were identified. Children with non-familial non-endocrine idiopathic short stature (ISS) (n=19, sequenced at the same laboratory followed by simultaneous data processing with HP patients), served as a control group. To assess the frequency of genetic (mono-, di-, or oligogenic) HP cases, we identified heterozygous variants (regardless of inheritance) in 42 genes previously reported to be associated with pituitary development. The average number of variants per proband was greater in HP than in ISS (1.1 vs 0.26, P = 0.04). Similarly, the number of probands with at least 1 variant in a pituitary-associated gene was greater in HP than in ISS (67% vs 21%, P = 0.035). These data suggest that sporadic hypopituitarism is frequently genetic. To assess the number of monogenic cases, we counted the number of candidate variants (in any gene in the genome, to capture undiscovered causes) that were inherited in a fashion that could explain the sporadic occurrence with a monogenic etiology (de novo mutation, autosomal recessive, X-linked recessive). There were fewer monogenic candidates in subjects with HP than ISS (1.6 vs 2.6 candidates/proband, P = 0.03). These data are consistent with approximately 1.6 non-causative variants/proband in both groups plus approximately 1 causative monogenic variant in ISS vs approximately 0 causative monogenic variants in HP. Candidate variants in genes previously reported to explain the phenotype were identified in 0 out of 9 trios with HP and in 8 of 19 trios with ISS (42%). These findings suggest that a monogenic inheritance is less common in HP than in ISS. In conclusion, the findings suggest that sporadic congenital hypopituitarism is frequently genetic but infrequently monogenic, implying a likely digenic/oligogenic etiology. ]]> <![CDATA[OR16-01 The Expression of the Homeodomain Transcription Factor SIX3 within Kisspeptin Neurons Is Necessary for Reproduction in Mice]]> <![CDATA[SAT-282 Hypothalamic Pituitary Adrenal Axis Hyperactivity in Db/db Mice]]> <![CDATA[SAT-299 Chronic Treatment Of Juvenile Hypothalamic Pomc-deficient Mice With RM-493 Prevents The Development Of Obesity]]> <![CDATA[SAT-293 Osteocalcin and Exercise Improve Mood and Cognition in Female Mice with High-Fat Diet Induced Type 2 Diabetes]]> <![CDATA[SAT-288 Pituitary Developmental Defects Caused by Haploinsufficiency for the Transcription Factor SIX3 Are Worsened by POU1F1 Deficiency]]> <![CDATA[OR16-06 Age-Associated Local GH Promotes Colon Neoplasia]]> <![CDATA[OR16-03 Metabolic Effects Of Hypothalamic Pomc Neurons Generated Postnatally From Tanycytes On A Pomc Null Genetic Background]]> <![CDATA[SAT-LB58 Molecular Investigation of Recessive Inheritance by Exome Sequencing of Patients With Congenital Hypopituitarism]]> A (p.Val289Ile). Only CDH2 is known to be expressed in the pituitary, and Pla2g4a null mice have a pleiotropic phenotype without obvious hypopituitarism. The CDH2 variant is rare and classified as deleterious. Sanger sequencing of CDH2 in four family members of the affected proband revealed that the unaffected parents and two unaffected siblings were heterozygous carriers. The effect of the CDH2 variant on cell aggregation was assessed in cell culture. Large cell aggregates formed in cells transfected with wild type CDH2, but cell aggregates were small or absent in cells that were either non-transfected or transfected with the CDH2 variant. Second, a patient with isolated GHD and no MRI abnormalities was identified with a rare, likely deleterious, homozygous GH1 c.171delT (p. Phe 57Leufs*43) variant. He had a sister who died at the age of 5 and had features of GHD. Conclusion: In a cohort of congenital hypopituitarism from consanguineous parents we had 15% molecular diagnosis using WES. We identified a variant in a known gene, GH1 c.171delT and a variant in a novel gene, CDH2 p.Val289I. ]]>