Increased transactivation associated with SOX3 polyalanine tract deletion in a patient with hypopituitarism

Case Report: A Novel Point Mutation of SOX3 in a Subject With Growth Hormone Deficiency, Hypogonadotrophic Hypogonadism, and Borderline Intellectual Disability

SOX3 is critical for the development of the pituitary, brain, and face, and SOX3 mutations may lead to hypopituitarism, intellectual disability, and craniofacial abnormalities. Common SOX3 mutations are duplications and deletions of the whole or part of SOX3, yet only a few cases with point mutations were reported by far. We present a case with growth retardation, small penis, and learning difficulty. Further assessment confirmed growth hormone deficiency, hypogonadotropic hypogonadism (HH), and borderline intellectual disability. He also responded well to gonadotropin-releasing hormone stimulation test, which suggests defects in the hypothalamus, contrary to previous studies that reported defects in the pituitary. A pathogenic frame-shift mutation of SOX3 was found. A heterogeneous missense mutation in SEMA3A was identified in this patient as well, which may also contribute to the development of HH. As far as we know, this is the first report that a frame-shift mutation of SOX3 constitutes rare genetic causes of HH and growth hormone deficiency. Whether mutations in these two genes act synergistically in the pathogenesis of the patient's phenotype remains to be further investigated. We believe that our case extends the phenotypic spectrum and genetic variability of SOX3 mutation.

Isolated growth hormone deficiency type IA due to a novel GH1 variant: a case report

Background

A case of isolated growth hormone deficiency type IA (IGHD IA) caused by novel compound heterozygous mutation in the GH1 gene was reported in this study, which aimed to provide insights that will benefit future diagnosis and treatment.

Case presentation

We analyzed and summarized the clinical data and genetic test results from a patient with IGHD admitted in March 2019 to the Department of Pediatrics Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology. We described the results from a 1-year-9-months old female, whose chief complaint was “growth retardation for more than one year”. Her birth length was 49.0 cm, and her birth weight was 3.05 kg. Suboptimal intake (breastfeeding) jaundice lasted for approximately two months following birth. When evaluated at the age of 1-year-9-months old, the patient’s height was 61.0 cm (− 7.24 SD), and her weight was 6.4 kg (− 1.50 SD). The patient’s physical characteristics included yellowish hair, large and unclosed anterior fontanelles, raised forehead, and a low and flat nose. The major abnormalities observed from the auxiliary examinations included low GH (< 0.05 μg/l), low IGF-1 (16.99 μg/l), and elevated TSH (6.97 mIU/l). Genetic testing revealed two heterozygous variants: a splicing mutation (NG_011676.1(NM_022560.4): c.10 + 1G>T, inherited from her mother) in intron 1 of the GH1 gene and a deletion that encompassed the same gene (chr17: 61973811–61996255, inherited from her father). After hormone replacement therapy with L-thyroxine and recombinant human GH (rhGH), the patient’s thyroid function returned to normal, and her serum IGF-1 level significantly improved, which resulted in an accelerated increase in height.

Conclusion

This study described a case of IGHD caused by novel compound heterozygous mutations in the GH1 gene. This study suggested that closer attention should be directed to genetic testing and diagnosis based on clinical characteristics to avoid misdiagnosis.

Evidence That the Etiology of Congenital Hypopituitarism Has a Major Genetic Component but Is Infrequently Monogenic

Purpose

Congenital hypopituitarism usually occurs sporadically. In most patients, the etiology remains unknown.

Methods

We studied 13 children with sporadic congenital hypopituitarism. Children with non-endocrine, non-familial idiopathic short stature (NFSS) (n = 19) served as a control group. Exome sequencing was performed in probands and both unaffected parents. A burden testing approach was used to compare the number of candidate variants in the two groups.

Results

First, we assessed the frequency of rare, predicted-pathogenic variants in 42 genes previously reported to be associated with pituitary gland development. The average number of variants per individual was greater in probands with congenital hypopituitarism than those with NFSS (1.1 vs. 0.21, mean variants/proband, P = 0.03). The number of probands with at least 1 variant in a pituitary-associated gene was greater in congenital hypopituitarism than in NFSS (62% vs. 21%, P = 0.03). Second, we assessed the frequency of rare, predicted-pathogenic variants in the exome (to capture undiscovered causes) that were inherited in a fashion that could explain the sporadic occurrence of the proband's condition with a monogenic etiology (de novo mutation, autosomal recessive, or X-linked recessive) with complete penetrance. There were fewer monogenic candidates in the probands with congenital hypopituitarism than those with NFSS (1.3 vs. 2.5 candidate variants/proband, P = 0.024). We did not find any candidate variants (0 of 13 probands) in genes previously reported to explain the phenotype in congenital hypopituitarism, unlike NFSS (8 of 19 probands, P = 0.01).

Conclusion

Our findings provide evidence that the etiology of sporadic congenital hypopituitarism has a major genetic component but may be infrequently monogenic with full penetrance, suggesting a more complex etiology.

Allelic Variants in Established Hypopituitarism Genes Expand Our Knowledge of the Phenotypic Spectrum

We report four allelic variants (three novel) in three genes previously established as causal for hypopituitarism or related disorders. A novel homozygous variant in the growth hormone gene, GH1 c.171delT (p.Phe 57Leufs*43), was found in a male patient with severe isolated growth hormone deficiency (IGHD) born to consanguineous parents. A hemizygous SOX3 allelic variant (p.Met304Ile) was found in a male patient with IGHD and hypoplastic anterior pituitary. YASARA, a tool to evaluate protein stability, suggests that p.Met304Ile destabilizes the SOX3 protein (ΔΔG = 2.49 kcal/mol). A rare, heterozygous missense variant in the TALE homeobox protein gene, TGIF1 (c.268C>T:p.Arg90Cys) was found in a patient with combined pituitary hormone deficiency (CPHD), diabetes insipidus, and syndromic features of holoprosencephaly (HPE). This variant was previously reported in a patient with severe holoprosencephaly and shown to affect TGIF1 function. A novel heterozygous TGIF1 variant (c.82T>C:p.Ser28Pro) was identified in a patient with CPHD, pituitary aplasia and ectopic posterior lobe. Both TGIF1 variants have an autosomal dominant pattern of inheritance with incomplete penetrance. In conclusion, we have found allelic variants in three genes in hypopituitarism patients. We discuss these variants and associated patient phenotypes in relation to previously reported variants in these genes, expanding our knowledge of the phenotypic spectrum in patient populations.

Congenital hypopituitarism in two brothers with a duplication of the 'acrogigantism gene' GPR101: clinical findings and review of the literature

PURPOSE

Congenital hypopituitarism (CH) can cause significant morbidity or even mortality. In the majority of patients, the etiology of CH is unknown. Understanding the etiology of CH is important for anticipation of clinical problems and for genetic counselling. Our previous studies showed that only a small proportion of cases have mutations in the known 'CH genes'. In the current project, we present the results of SNP array based copy number variant analysis in a family with unexplained congenital hypopituitarism.

METHODS

DNA samples of two affected brothers with idiopathic CH and their mother were simultaneously analyzed by SNP arrays for copy number variant analysis and Whole Exome Sequencing (WES) for mutation screening. DNA of the father was not available.

RESULTS

We found a 6 Mb duplication including GPR101 and SOX3 on the X-chromosome (Xq26.2-q27.1) in the two siblings and their mother, leading to 2 copies of this region in the affected boys and 3 copies in the mother. Duplications of GPR101 are associated with X-linked acrogigantism (the phenotypic 'opposite' of the affected brothers), whereas alterations in SOX3 are associated with X-linked hypopituitarism.

CONCLUSION

In our patients with hypopituitarism we found a 6 Mb duplication which includes GPR101, a gene associated with X- linked gigantism, and SOX3, a gene involved in early pituitary organogenesis that is associated with variable degrees of hypopituitarism. Our findings show that in duplications containing both GPR101 and SOX3, the growth hormone deficiency phenotype is dominant. This suggests that, if GPR101 is duplicated, it might not be expressed phenotypically when early patterning of the embryonic pituitary is affected due to SOX3 duplication. These results, together with the review of the literature, shed a new light on the role of GPR101 and SOX3 in pituitary function.

Xq27.1 Duplication Encompassing SOX3: Variable Phenotype and Smallest Duplication Associated with Hypopituitarism to Date - A Large Case Series of Unrelated Patients and a Literature Review

BACKGROUND

Xq27.1 duplication encompassing SOX3 has been implicated in the aetiology of X-linked hypopituitarism associated with intellectual disability and neural tube defects. We describe the largest case series to date of 5 unrelated patients with SOX3 duplication with a variable clinical phenotype, including the smallest reported SOX3 duplication.

CASE REPORTS

Five male patients who presented with congenital hypopituitarism (CH) were identified to have Xq27.1 duplication encompassing SOX3. The size of the duplication ranged from 323.8 kb to 11 Mb. The duplication was maternally inherited or de novo in 2 patients each (and of unknown inheritance in 1 patient). The age at presentation was variable. Three patients had multiple pituitary hormone deficiencies, whereas 2 patients had isolated growth hormone deficiency. All patients had micropenis and/or small undescended testes. Structural pituitary and/or other midline cranial abnormalities (callosal hypogenesis/absence of the septum pellucidum) were present in all patients. Two patients had a neural tube defect in addition to CH.

CONCLUSIONS

This is the largest series reported to date of unrelated patients with CH in association with Xq27.1 duplication encompassing SOX3. The clinical phenotype is variable, which may be due to genetic redundancy or other unknown aetiological factors. We have expanded the phenotypic spectrum through description of the smallest Xq27.1 duplication (323.8 kb) with CH reported to date, as well as a second family with CH and a neural tube defect.

The Molecular Basis of Congenital Hypopituitarism and Related Disorders

CONTEXT

Congenital hypopituitarism (CH) is characterized by the presence of deficiencies in one or more of the 6 anterior pituitary (AP) hormones secreted from the 5 different specialized cell types of the AP. During human embryogenesis, hypothalamo-pituitary (HP) development is controlled by a complex spatio-temporal genetic cascade of transcription factors and signaling molecules within the hypothalamus and Rathke's pouch, the primordium of the AP.

EVIDENCE ACQUISITION

This mini-review discusses the genes and pathways involved in HP development and how mutations of these give rise to CH. This may present in the neonatal period or later on in childhood and may be associated with craniofacial midline structural abnormalities such as cleft lip/palate, visual impairment due to eye abnormalities such as optic nerve hypoplasia (ONH) and microphthalmia or anophthalmia, or midline forebrain neuroradiological defects including agenesis of the septum pellucidum or corpus callosum or the more severe holoprosencephaly.

EVIDENCE SYNTHESIS

Mutations give rise to an array of highly variable disorders ranging in severity. There are many known causative genes in HP developmental pathways that are routinely screened in CH patients; however, over the last 5 years this list has rapidly increased due to the identification of variants in new genes and pathways of interest by next-generation sequencing.

CONCLUSION

The majority of patients with these disorders do not have an identified molecular basis, often making management challenging. This mini-review aims to guide clinicians in making a genetic diagnosis based on patient phenotype, which in turn may impact on clinical management.

Genetics of congenital hypogonadotropic hypogonadism: peculiarities and phenotype of an oligogenic disease

A genetic basis of congenital isolated hypogonadotropic hypogonadism (CHH) can be defined in almost 50% of cases, albeit not necessarily the complete genetic basis. Next-generation sequencing (NGS) techniques have led to the discovery of a great number of loci, each of which has illuminated our understanding of human gonadotropin-releasing hormone (GnRH) neurons, either in respect of their embryonic development or their neuroendocrine regulation as the "pilot light" of human reproduction. However, because each new gene linked to CHH only seems to underpin another small percentage of total patient cases, we are still far from achieving a comprehensive understanding of the genetic basis of CHH. Patients have generally not benefited from advances in genetics in respect of novel therapies. In most cases, even genetic counselling is limited by issues of apparent variability in expressivity and penetrance that are likely underpinned by oligogenicity in respect of known and unknown genes. Robust genotype-phenotype relationships can generally only be established for individuals who are homozygous, hemizygous or compound heterozygotes for the same gene of variant alleles that are predicted to be deleterious. While certain genes are purely associated with normosmic CHH (nCHH) some purely with the anosmic form (Kallmann syndrome-KS), other genes can be associated with both nCHH and KS-sometimes even within the same kindred. Even though the anticipated genetic overlap between CHH and constitutional delay in growth and puberty (CDGP) has not materialised, previously unanticipated genetic relationships have emerged, comprising conditions of combined (or multiple) pituitary hormone deficiency (CPHD), hypothalamic amenorrhea (HA) and CHARGE syndrome. In this review, we report the current evidence in relation to phenotype and genetic peculiarities regarding 60 genes whose loss-of-function variants can disrupt the central regulation of reproduction at many levels: impairing GnRH neurons migration, differentiation or activation; disrupting neuroendocrine control of GnRH secretion; preventing GnRH neuron migration or function and/or gonadotropin secretion and action.

Development of the Pituitary Gland

The development of the anterior pituitary gland occurs in distinct sequential developmental steps, leading to the formation of a complex organ containing five different cell types secreting six different hormones. During this process, the temporal and spatial expression of a cascade of signaling molecules and transcription factors plays a crucial role in organ commitment, cell proliferation, patterning, and terminal differentiation. The morphogenesis of the gland and the emergence of distinct cell types from a common primordium are governed by complex regulatory networks involving transcription factors and signaling molecules that may be either intrinsic to the developing pituitary or extrinsic, originating from the ventral diencephalon, the oral ectoderm, and the surrounding mesenchyme. Endocrine cells of the pituitary gland are organized into structural and functional networks that contribute to the coordinated response of endocrine cells to stimuli; these cellular networks are formed during embryonic development and are maintained or may be modified in adulthood, contributing to the plasticity of the gland. Abnormalities in any of the steps of pituitary development may lead to congenital hypopituitarism that includes a spectrum of disorders from isolated to combined hormone deficiencies including syndromic disorders such as septo-optic dysplasia. Over the past decade, the acceleration of next-generation sequencing has allowed for rapid analysis of the patient genome to identify novel mutations and novel candidate genes associated with hypothalmo-pituitary development. Subsequent functional analysis using patient fibroblast cells, and the generation of stem cells derived from patient cells, is fast replacing the need for animal models while providing a more physiologically relevant characterization of novel mutations. Furthermore, CRISPR-Cas9 as the method for gene editing is replacing previous laborious and time-consuming gene editing methods that were commonly used, thus yielding knockout cell lines in a fraction of the time. © 2020 American Physiological Society. Compr Physiol 10:389-413, 2020.

Pituitary Transcription Factor Mutations Leading to Hypopituitarism

Congenital pituitary hormone deficiency is a disabling condition. It is part of a spectrum of disorders including craniofacial midline developmental defects ranging from holoprosencephaly through septo-optic dysplasia to combined and isolated pituitary hormone deficiency. The first genes discovered in the human disease were based on mouse models of dwarfism due to mutations in transcription factor genes. High-throughput DNA sequencing technologies enabled clinicians and researchers to find novel genetic causes of hypopituitarism for the more than three quarters of patients without a known genetic diagnosis to date. Transcription factor (TF) genes are at the forefront of the functional analysis of novel variants of unknown significance due to the relative ease in in vitro testing in a research lab. Genetic testing in hypopituitarism is of high importance to the individual and their family to predict phenotype composition, disease progression and to avoid life-threatening complications such as secondary adrenal insufficiency.This chapter aims to highlight our current understanding about (1) the contribution of TF genes to pituitary development (2) the diversity of inheritance and phenotype features in combined and select isolated pituitary hormone deficiency and (3) provide an initial assessment on how to approach variants of unknown significance in human hypopituitarism. Our better understanding on how transcription factor gene variants lead to hypopituitarism is a meaningful step to plan advanced therapies to specific genetic changes in the future.

Increased transactivation and impaired repression of β-catenin-mediated transcription associated with a novel SOX3 missense mutation in an X-linked hypopituitarism pedigree with modest growth failure

SOX3, a transcription factor of the SRY-related high mobility group box family, has been implicated in the etiology of X-linked hypopituitarism. Here, we report a Chinese pedigree of X-linked hypopituitarism with variable phenotypes. Despite the complete growth hormone deficiency, the growth failure of the patients was relatively modest. A rare point variant of SOX3 (c.424C > A; p. P142T) was identified in the pedigree via target panel sequencing. An in vitro study showed that both the expression and nuclear targeting of SOX3 remained unaffected by the variant. However, increased transcriptional activation and impaired repression of β-catenin-mediated transcription were noticed as a result of the SOX3 variant. This is the first study to report that the rare SOX3 missense variant associated with hypopituitarism possibly due to increased activation of SOX3 target genes and disregulation of β-catenin target genes. In addition, we have expanded the phenotypic spectrum associated with SOX3 mutations.

A complex phenotype in a family with a pathogenic SOX3 missense variant

Duplications and deletions of Xq26-27 including SOX3 (Xq27.1) have been associated with X-linked mental retardation and isolated growth hormone deficiency (OMIM 300123) or X-linked panhypopituitarism (OMIM 312000). Yet, pathogenic point mutations seem to be extremely rare. We report a family with three affected males with several clinical features including mild intellectual disability, microphthalmia, coloboma, hypopituitarism, facial dysmorphology and dental anomalies, including microcephaly, retrognathia and a solitary median maxillary central incisor amongst other features. Using Whole Exome Sequencing a missense variant in SOX3, NM_005634.2:c.449C>A; p.(Ser150Tyr) was identified. Segregation analysis in the family demonstrated that the variant was inherited through healthy females with its origin in the maternal grandmother showing germline mosaicism. Thus, we report one of the first cases of a pathogenic variant in SOX3 and germline mosaicism of this variant.

Detection of an Inherited Deletion in Products of Conception in a Patient With Recurrent Losses and Normal Karyotype

BACKGROUND

Microarray analysis testing on products of conception can provide valuable information in the evaluation of recurrent pregnancy loss beyond ploidy status.

CASE

A maternally inherited deletion on the X chromosome was detected by microarray analysis performed on products of conception in a couple with recurrent pregnancy loss. The mother had a previously demonstrated normal karyotype with standard cytogenetic analysis but was subsequently determined to have the same X chromosome deletion by oligonucleotide single-nucleotide polymorphism (SNP) microarray analysis.

CONCLUSION

Direct testing of products of conception using oligonucleotide SNP microarray identified a maternally inherited microdeletion on the X chromosome in a patient with recurrent losses and normal karyotype. Going forward, the couple may use preimplantation genetic diagnosis testing to identify embryos free of this deletion for transfer.

Next generation sequencing and array-based comparative genomic hybridization for molecular diagnosis of pediatric endocrine disorders

Next-generation sequencing (NGS) and array-based comparative genomic hybridization (array CGH) have enabled us to perform high-throughput mutation screening and genome-wide copy number analysis, respectively. These methods can be used for molecular diagnosis of pediatric endocrine disorders. NGS has determined the frequency and phenotypic variation of mutations in several disease-associated genes. Furthermore, whole exome analysis using NGS has successfully identified several novel causative genes for endocrine disorders. Array CGH is currently used as the standard procedure for molecular cytogenetic analysis. Array CGH can detect various submicroscopic genomic rearrangements involving exons or enhancers of disease-associated genes. This review introduces some examples of the use of NGS and array CGH for the molecular diagnosis of pediatric endocrine disorders.

Expanded polyalanine tracts function as nuclear export signals and promote protein mislocalization via eEF1A1 factor

Polyalanine (poly(A)) diseases are caused by the expansion of translated GCN triplet nucleotide sequences encoding poly(A) tracts in proteins. To date, nine human disorders have been found to be associated with poly(A) tract expansions, including congenital central hypoventilation syndrome and oculopharyngeal muscular dystrophy. Previous studies have demonstrated that unexpanded wild-type poly(A)-containing proteins localize to the cell nucleus, whereas expanded poly(A)-containing proteins primarily localize to the cytoplasm. Because most of these poly(A) disease proteins are transcription factors, this mislocalization causes cellular transcriptional dysregulation leading to cellular dysfunction. Correcting this faulty localization could potentially point to strategies to treat the aforementioned disorders, so there is a pressing need to identify the mechanisms underlying the mislocalization of expanded poly(A) protein. Here, we performed a glutathione S-transferase pulldown assay followed by mass spectrometry and identified eukaryotic translation elongation factor 1 α1 (eEF1A1) as an interacting partner with expanded poly(A)-containing proteins. Strikingly, knockdown of eEF1A1 expression partially corrected the mislocalization of the expanded poly(A) proteins in the cytoplasm and restored their functions in the nucleus. We further demonstrated that the expanded poly(A) domain itself can serve as a nuclear export signal. Taken together, this study demonstrates that eEF1A1 regulates the subcellular location of expanded poly(A) proteins and is therefore a potential therapeutic target for combating the pathogenesis of poly(A) diseases.

Genetics of Combined Pituitary Hormone Deficiency: Roadmap into the Genome Era

The genetic basis for combined pituitary hormone deficiency (CPHD) is complex, involving 30 genes in a variety of syndromic and nonsyndromic presentations. Molecular diagnosis of this disorder is valuable for predicting disease progression, avoiding unnecessary surgery, and family planning. We expect that the application of high throughput sequencing will uncover additional contributing genes and eventually become a valuable tool for molecular diagnosis. For example, in the last 3 years, six new genes have been implicated in CPHD using whole-exome sequencing. In this review, we present a historical perspective on gene discovery for CPHD and predict approaches that may facilitate future gene identification projects conducted by clinicians and basic scientists. Guidelines for systematic reporting of genetic variants and assigning causality are emerging. We apply these guidelines retrospectively to reports of the genetic basis of CPHD and summarize modes of inheritance and penetrance for each of the known genes. In recent years, there have been great improvements in databases of genetic information for diverse populations. Some issues remain that make molecular diagnosis challenging in some cases. These include the inherent genetic complexity of this disorder, technical challenges like uneven coverage, differing results from variant calling and interpretation pipelines, the number of tolerated genetic alterations, and imperfect methods for predicting pathogenicity. We discuss approaches for future research in the genetics of CPHD.

Identification of an IGSF1-specific deletion in a five-generation pedigree with X-linked Central Hypothyroidism without macroorchidism

OBJECTIVES

IGSF1 deficiency syndrome (IDS) is a recently described X-linked congenital central hypothyroidism disorder characterized by loss-of-function mutations in the immunoglobulin superfamily member 1 (IGSF1) gene. The phenotypic spectrum and intrafamilial variability associated with IDS remain unclear due to a paucity of large, well-characterized pedigrees. Here, we present phenotypic analysis and molecular characterization of a five-generation pedigree with IGSF1 deficiency containing 10 affected males.

PATIENTS AND METHODS

Pituitary function was assessed in all available family members (n = 8 affected males and n = 5 carrier females). Molecular characterization of the family was performed by Sanger sequencing of PCR products amplified from the IGSF1 locus and by array comparative genomic hybridization.

RESULTS

A 42-kb IGSF1 deletion spanning the entire coding sequence was identified in all affected males. TSH deficiency, although subclinical in one case, was identified in all affected males (n = 8). PRL and GH deficiency were also present in 5 of 6 and 4 of 8 affected males, respectively. In contrast to previous reports, macroorchidism was not detected in any of the four affected males who were examined for this feature. Only 1 of 5 carrier females had pituitary dysfunction (TSH and GH deficiency).

CONCLUSION

Individuals with identical IGSF1 deletions can exhibit variable pituitary hormone deficiencies, of which overt TSH deficiency is the most consistent feature. We also show that macroorchidism is not obligatory in males with IDS. Mutations of IGSF1 should therefore be considered in males with isolated hypopituitarism that includes TSH deficiency.

SOX3 Overdosage Permits Normal Sex Development in Females with Random X Inactivation

Submicroscopic duplications involving SOX3 and/or its flanking regions have been identified in 46,XX individuals both with and without disorders of sex development, raising the question whether SOX3 overdosage is sufficient to induce testicular development in genetically female individuals. Here, we report a mother-daughter pair with female phenotypes and random X inactivation. The individuals carry complex X chromosomal rearrangements leading to a copy number gain of genomic regions involving SOX3 and its upstream region. The amplified DNA fragments were detected at Xq27. These results provide evidence that SOX3 overdosage permits normal sex development in 46,XX individuals with random X inactivation.

Neuroendocrine causes of amenorrhea--an update

CONTEXT

Secondary amenorrhea--the absence of menses for three consecutive cycles--affects approximately 3-4% of reproductive age women, and infertility--the failure to conceive after 12 months of regular intercourse--affects approximately 6-10%. Neuroendocrine causes of amenorrhea and infertility, including functional hypothalamic amenorrhea and hyperprolactinemia, constitute a majority of these cases.

OBJECTIVE

In this review, we discuss the physiologic, pathologic, and iatrogenic causes of amenorrhea and infertility arising from perturbations in the hypothalamic-pituitary-adrenal axis, including potential genetic causes. We focus extensively on the hormonal mechanisms involved in disrupting the hypothalamic-pituitary-ovarian axis.

CONCLUSIONS

A thorough understanding of the neuroendocrine causes of amenorrhea and infertility is critical for properly assessing patients presenting with these complaints. Prompt evaluation and treatment are essential to prevent loss of bone mass due to hypoestrogenemia and/or to achieve the time-sensitive treatment goal of conception.

A novel mutation in SOX3 polyalanine tract: a case of Kabuki syndrome with combined pituitary hormone deficiency harboring double mutations in MLL2 and SOX3

INTRODUCTION

Both duplications encompassing SOX3 and loss-of function mutations in SOX3 have been reported in a minor portion of X-linked isolated growth hormone deficiency (GHD) or combined pituitary hormone deficiency (CPHD) patients with or without mental retardation.

PATIENTS AND METHODS

We report a Japanese male patient with molecularly confirmed Kabuki syndrome who was found to have CPHD. We analyzed all coding exons and flanking introns of currently known nine genes responsible for CPHD by PCR-based sequencing.

RESULTS

In this CPHD patient, we identified a novel hemizygous 21-base pair deletion, resulting in the loss of 7 alanine residues from polyalanine (PA) tracts of SOX3. The clinically and endocrinologically normal mother of the patient carried the same deletion in a heterozygous manner. In vitro experiments showed that the del 7A SOX3 had increased transactivation of the HESX1 promoter.

CONCLUSION

Our study provides additional evidence that deletion in PA tracts of SOX3 is associated with hypopituitarism. Female carriers of SOX3 PA tract deletions will show a broad phenotypic spectrum, ranging from clinically normal to CPHD.

Isolated growth hormone deficiency (GHD) in childhood and adolescence: recent advances

The diagnosis of GH deficiency (GHD) in childhood is a multistep process involving clinical history, examination with detailed auxology, biochemical testing, and pituitary imaging, with an increasing contribution from genetics in patients with congenital GHD. Our increasing understanding of the factors involved in the development of somatotropes and the dynamic function of the somatotrope network may explain, at least in part, the development and progression of childhood GHD in different age groups. With respect to the genetic etiology of isolated GHD (IGHD), mutations in known genes such as those encoding GH (GH1), GHRH receptor (GHRHR), or transcription factors involved in pituitary development, are identified in a relatively small percentage of patients suggesting the involvement of other, yet unidentified, factors. Genome-wide association studies point toward an increasing number of genes involved in the control of growth, but their role in the etiology of IGHD remains unknown. Despite the many years of research in the area of GHD, there are still controversies on the etiology, diagnosis, and management of IGHD in children. Recent data suggest that childhood IGHD may have a wider impact on the health and neurodevelopment of children, but it is yet unknown to what extent treatment with recombinant human GH can reverse this effect. Finally, the safety of recombinant human GH is currently the subject of much debate and research, and it is clear that long-term controlled studies are needed to clarify the consequences of childhood IGHD and the long-term safety of its treatment.

Evidence for increased SOX3 dosage as a risk factor for X-linked hypopituitarism and neural tube defects

Genomic duplications of varying lengths at Xq26-q27 involving SOX3 have been described in families with X-linked hypopituitarism. Using array-CGH we detected a 1.1 Mb microduplication at Xq27 in a large family with three males suffering from X-linked hypopituitarism. The duplication was mapped from 138.7 to 139.8 Mb, harboring only two annotated genes, SOX3 and ATP11C, and was shown to be a direct tandem copy number gain. Unexpectedly, the microduplication did not fully segregate with the disease in this family suggesting that SOX3 duplications have variable penetrance for X-linked hypopituitarism. In the same family, a female fetus presenting with a neural tube defect was also shown to carry the SOX3 copy number gain. Since we also demonstrated increased SOX3 mRNA levels in amnion cells derived from an unrelated t(X;22)(q27;q11) female fetus with spina bifida, we propose that increased levels of SOX3 could be a risk factor for neural tube defects.

Pituitary stalk interruption syndrome in 58 Chinese patients: clinical features and genetic analysis

OBJECTIVES

Pituitary stalk interruption syndrome (PSIS) is rare and its clinical features and pathogenesis are poorly understood. This study characterized the clinical and genetic features of PSIS in Chinese patients.

DESIGN AND PATIENTS

Clinical data of 58 patients with PSIS and 46 patients with GH deficiency but a normal pituitary stalk (NPS) were retrospectively analysed. HESX1, LHX4, OTX2 and SOX3 polymorphisms were screened in 33 PSIS patients, and GH1 and GHRHR in 4 NPS patients.

RESULTS

Deficiency of GH was 100% in both PSIS and NPS groups. Other deficiency rates for PSIS and NPS groups were as follows: ACTH, 77·6% and 23·9%; TSH, 43·1% and 10·9%; LH/FSH, 94·2% and 47·4%; and combined pituitary hormone, 93·1% and 41·3% respectively. In PSIS and NPS patients, the percentages of anterior pituitary hypoplasia were 98·3% and 54·3%, pituitary stalk abnormality were 100% and 0%, and ectopic neurohypophysis were 91·4% and 0%. A novel heterozygous sequence variant (c.142A>T, p.T48S) was found in HESX1 in one PSIS patient, 3 polymorphisms (c.63T>C, p.G21G; c.450C>T, p.N150N; and c.983A>G, p.N328S) in LHX4 in 7, 1 and 31 PSIS patients, respectively, and a hemizygous polymorphism (c.157G>C, p.V53L) in SOX3 in one PSIS patient. No OTX2 abnormality was detected in PSIS patients, and no GH1 or GHRHR polymorphisms in NPS patients.

CONCLUSIONS

Compared with NPS, PSIS patients had more severe anterior pituitary hormone deficiency, lower anterior pituitary hormone secretion and higher probability of abnormal pituitary morphology. HESX1, LHX4 and SOX3 polymorphisms may be associated with PSIS.

Mechanistic insight into the pathology of polyalanine expansion disorders revealed by a mouse model for X linked hypopituitarism

Polyalanine expansions in transcription factors have been associated with eight distinct congenital human diseases. It is thought that in each case the polyalanine expansion causes misfolding of the protein that abrogates protein function. Misfolded proteins form aggregates when expressed in vitro; however, it is less clear whether aggregation is of relevance to these diseases in vivo. To investigate this issue, we used targeted mutagenesis of embryonic stem (ES) cells to generate mice with a polyalanine expansion mutation in Sox3 (Sox3-26ala) that is associated with X-linked Hypopituitarism (XH) in humans. By investigating both ES cells and chimeric mice, we show that endogenous polyalanine expanded SOX3 does not form protein aggregates in vivo but rather is present at dramatically reduced levels within the nucleus of mutant cells. Importantly, the residual mutant protein of chimeric embryos is able to rescue a block in gastrulation but is not sufficient for normal development of the hypothalamus, a region that is functionally compromised in Sox3 null embryos and individuals with XH. Together, these data provide the first definitive example of a disease-relevant PA mutant protein that is both nuclear and functional, thereby manifesting as a partial loss-of-function allele.

Single-nucleotide variants in two Hedgehog genes, SHH and HHIP, as genetic cause of combined pituitary hormone deficiency

OBJECTIVE

Combined pituitary hormone deficiency (CPHD) is characterized by deficiencies of two or more anterior pituitary hormones. Its genetic cause is unknown in the majority of cases. The Hedgehog (Hh) signalling pathway has been implicated in disorders associated with pituitary development. Mutations in Sonic Hedgehog (SHH) have been described in patients with holoprosencephaly (with or without pituitary involvement). Hedgehog interacting protein (HHIP) has been associated with variations in adult height in genome wide association studies. We investigated whether mutations in these two genes of the Hh pathway, SHH and HHIP, could result in 'idiopathic' CPHD.

DESIGN/PATIENTS

We directly sequenced the coding regions and exon - intron boundaries of SHH and HHIP in 93 CPHD patients of the Dutch HYPOPIT study in whom mutations in the classical CPHD genes PROP1, POU1F1, HESX1, LHX3 and LHX4 had been ruled out. We compared the expression of Hh genes in Hep3B transfected cells between wild-type proteins and mutants.

RESULTS

We identified three single-nucleotide variants (p.Ala226Thr, c.1078C>T and c.*8G>T) in SHH. The function of the latter was severely affected in our in vitro assay. In HHIP, we detected a new activating variant c.-1G>C, which increases HHIP's inhibiting function on the Hh pathway.

CONCLUSIONS

Our results suggest involvement of the Hedgehog pathway in CPHD. We suggest that both SHH and HHIP are investigated as a second screening in CPHD, after mutations in the classical CPHD genes have been ruled out.

Molecular pathology of polyalanine expansion disorders: new perspectives from mouse models

Disease-causing polyalanine (PA) expansion mutations have been identified in nine genes, eight of which encode transcription factors (TFs) with important roles in development. In vitro and cell overexpression studies have shown that expanded PA tracts result in protein misfolding and the formation of aggregates. This feature of PA proteins is reminiscent of the related polyglutamine (PQ) disease proteins, which have been shown to cause disease via a gain-of-function (GOF) mechanism. However, in sharp contrast to PQ disorders, the disease phenotypes associated with PA mutations are more consistent with a LOF and/or mild GOF mechanism, suggesting that their molecular pathology is inherently different to PQ disorders. Elucidating the cellular impact of PA mutations in vivo has been difficult to address as, unlike the late-onset polyglutamine disorders, all PA disorders associated with TF gene mutations are congenital. However, in recent years, significant advances have been made through the analysis of engineered (knock-in) and spontaneous PA mouse models. Here we review these recent findings and propose an updated model of the molecular and cellular mechanism of PA disorders that incorporates both LOF and GOF features.

Genetic disorders of the pituitary

PURPOSE OF REVIEW

To discuss pituitary development and function related to those factors in which molecular defects resulting in combined pituitary hormone deficiency have been described in humans, and to describe recently reported novel mutations in these factors (January 2010 to September 2011).

RECENT FINDINGS

Novel mutations have been found in transcription factors involved in pituitary development, HESX1; LHX3; LHX4; SOX3; Prophet of Pit-1; and POU1FI, and in some of the signaling molecules expressed in the ventral diencephalon (fibroblast growth factor 8 and GLI2). There is phenotypic variability for the same mutation suggesting variable penetrance due to other genetic, epigenetic, or environmental factors. The incidence of mutations in these factors is low suggesting that other genes or environmental factors are responsible for the majority of cases of combined pituitary hormone deficiency.

SUMMARY

Development of the pituitary gland and pituitary cell determination and specification depend on the expression and interaction of signaling molecules and transcription factors in overlapping, but distinct, spatial and temporal patterns. Studying genotype-phenotype correlations in patients with mutations in these factors give insight into the mechanisms involved in normal pituitary development and function.

Phenotype-genotype correlations in congenital isolated growth hormone deficiency (IGHD)

Isolated growth hormone deficiency (IGHD) may be congenital, often due to genetic mutations, or acquired as a result of other factors such as cranial irradiation. The commonest genes implicated in its genetic etiology are those encoding growth hormone (GH1) and the receptor for GH-releasing hormone (GHRHR). Rarely, IGHD may be caused by mutations in transcription factors (HESX1, SOX3, OTX2) or be the first presentation before the development of other pituitary hormone deficiencies. IGHD has been classified in four genetic forms (type IA, IB, II and III). Despite the increasing number of genes implicated in the etiology of IGHD, mutations in known genes account only for a small percentage of cases; therefore, other as yet unidentified factors may be implicated in its etiology. Although there is no strict genotype/phenotype correlation in patients with IGHD, there are some emerging patterns that may guide us towards a genetic diagnosis of the condition. There is increasing understanding that the phenotype of patients with IGHD is highly variable and sometimes even evolving, dictating the need for long term follow-up in these cases.