Heterozygous orthodenticle homeobox 2 mutations are associated with variable pituitary phenotype

An Orthodenticle Homeobox 2 (OTX2) Mutation in a Patient With Combined Pituitary Hormone Deficiency, Pituitary Malformation, and Retinitis Pigmentosa

Heterozygous mutations of orthodenticle homeobox 2 (OTX2)can result in ocular malformations, pituitary abnormalities, or hypopituitarism spanning from isolated growth hormone (GH) deficiency to combined pituitary hormone deficiency. We present a patient exhibiting growth and pubertal disturbances, developmental delay, and pigmentary retinopathy. Further examination revealed deficiencies in GH following clonidine stimulation, hypogonadism, and, subsequently, central hypothyroidism. Brain magnetic resonance imaging uncovered hypoplasia of the pituitary and an ectopic pituitary tissue. Sequence analysis of OTX2 identified a novel heterozygous mutation c.555_556dup, p.(Ser186Ilefs*21), indicative of a frameshift mutation. Replacement therapy with recombinant human GH, testosterone enanthate, and levothyroxine was started. Notably, GH therapy resulted in significant catch-up growth. This case report contributes to our comprehension of the molecular and clinical findings, particularly highlighting endocrine manifestations and a rare ophthalmologic manifestation associated with mutations in the OTX2 gene.

OTX Genes in Adult Tissues

OTX homeobox genes have been extensively studied for their role in development, especially in neuroectoderm formation. Recently, their expression has also been reported in adult physiological and pathological tissues, including retina, mammary and pituitary glands, sinonasal mucosa, in several types of cancer, and in response to inflammatory, ischemic, and hypoxic stimuli. Reactivation of OTX genes in adult tissues supports the notion of the evolutionary amplification of functions of genes by varying their temporal expression, with the selection of homeobox genes from the "toolbox" to drive or contribute to different processes at different stages of life. OTX involvement in pathologies points toward these genes as potential diagnostic and/or prognostic markers as well as possible therapeutic targets.

Combined pituitary hormone deficiency harboring CHD7 gene missense mutation without CHARGE syndrome: a case report

BACKGROUND

Heterozygous loss-of-function mutations in the chromodomain helicase DNA-binding protein 7 (CHD7) gene cause CHARGE syndrome characterized by various congenital anomalies. A majority of patients with CHARGE syndrome present with congenital hypogonadotropic hypogonadism (HH), and combined pituitary hormone deficiency (CPHD) can also be present. Whereas CHD7 mutations have been identified in some patients with isolated HH without a diagnosis of CHARGE syndrome, it remains unclear whether CHD7 mutations can be identified in patients with CPHD who do not fulfill the criteria for CHARGE syndrome.

CASE PRESENTATION

A 33-year-old woman was admitted to our hospital. She had primary amenorrhea and was at Tanner stage 2 for both pubic hair and breast development. She was diagnosed with CPHD (HH, growth hormone deficiency, and central hypothyroidism), and a heterozygous rare missense mutation (c.6745G > A, p.Asp2249Asn) in the CHD7 gene was identified. Our conservation analysis and numerous in silico analyses suggested that this mutation had pathogenic potential. She had mild intellectual disability, a minor feature of CHARGE syndrome, but did not fulfill the criteria for CHARGE syndrome.

CONCLUSIONS

We report a rare case of CPHD harboring CHD7 mutation without CHARGE syndrome. This case provides valuable insights into phenotypes caused by CHD7 mutations. CHD7 mutations can have a continuous phenotypic spectrum depending on the severity of hypopituitarism and CHARGE features. Therefore, we would like to propose a novel concept of CHD7-associated syndrome.

Growth hormone deficiency in a case of septo-optic-dysplasia due to SOX2 mutation: should we re-test patients during the transition period?

Gene mutations encoding transcription factors, including SOX2, have been associated with growth hormone deficiency (GHD) and abnormal pituitary development. Guidelines on GHD management in the transition period state that patients with genetic-based childhood-onset GHD can skip retesting due to a high likelihood of permanent GHD. We describe a case of septo-optic-dysplasia due to SOX2 mutation characterised by childhood-onset GHD, which showed a normal somatotropic function at the transition period. This case raises the opportunity to retest for GHD during the transition period, even in patients with a known genetic cause, in order to avoid inappropriate GH treatment.

Genetic Regulation of Vertebrate Forebrain Development by Homeobox Genes

Forebrain development in vertebrates is regulated by transcription factors encoded by homeobox, bHLH and forkhead gene families throughout the progressive and overlapping stages of neural induction and patterning, regional specification and generation of neurons and glia from central nervous system (CNS) progenitor cells. Moreover, cell fate decisions, differentiation and migration of these committed CNS progenitors are controlled by the gene regulatory networks that are regulated by various homeodomain-containing transcription factors, including but not limited to those of the Pax (paired), Nkx, Otx (orthodenticle), Gsx/Gsh (genetic screened), and Dlx (distal-less) homeobox gene families. This comprehensive review outlines the integral role of key homeobox transcription factors and their target genes on forebrain development, focused primarily on the telencephalon. Furthermore, links of these transcription factors to human diseases, such as neurodevelopmental disorders and brain tumors are provided.

Identification of a novel de novo variant in OTX2 in a patient with congenital microphthalmia using targeted next-generation sequencing followed by prenatal diagnosis

BACKGROUND

Next-generation sequencing has been proven to be a reliable method for the detection of genetic causes in heterogeneous ocular disorders. In this report an NGS-based diagnostic approach was taken to uncover the genetic etiology in a patient with coloboma and microphthalmia, a highly heterogeneous disease with intrafamilial phenotypic variability.

MATERIALS AND METHODS

Next generation sequencing using a targeted panel of 316 genes, was carried out in the proband. Prioritized variants were then identified and confirmed using Sanger sequencing. Prenatal diagnosis of the detected variant was then performed in the family.

RESULTS

A novel de novo frameshift variant c.157_164delTTCACTCG (p.Phe53fs) in OTX2, leading to a truncated protein, was identified. Prenatal diagnosis identified the same variant in the fetus.

CONCLUSIONS

This report demonstrates the importance of genetic counseling and underscores the efficiency and effectiveness of targeted NGS as a means of detecting variants in inherited eye disorders.

Anophthalmia, Global Developmental Delay, and Severe Dysphagia in a Young Girl With 14q22q23 Microdeletion Syndrome

14q22q23 microdeletion syndrome, also called Frias syndrome, is an extremely rare partial deletion of the long arm of chromosome 14 characterized by the anomalies of the pituitary gland, eyes, and hand/foot. Intellectual disability and facial dysmorphism are other common manifestations. Haploinsufficiency of the genes bone morphogenetic protein 4 (BMP4) and orthodenticle homeobox 2 (OTX2) accounts for most of the phenotypic abnormalities seen in these patients. There are only a few cases reported with Frias syndrome in the literature, and there are multiple variations present, which are not well recognized due to different set of genes involved. This case report presents the case of a young child with a deletion in 14q22.2q23.1 region containing both BMP4 and OTX2 genes as well as sineoculis homeobox homolog 1 (SIX1) and sineoculis homeobox homolog 6 (SIX6) genes. The case report illustrates the wide phenotypic findings associated with these genes along with additional unique findings that previously have not been commonly reported.

Otx2b mutant zebrafish have pituitary, eye and mandible defects that model mammalian disease

Combined pituitary hormone deficiency (CPHD) is a genetically heterogeneous disorder caused by mutations in over 30 genes. The loss-of-function mutations in many of these genes, including orthodenticle homeobox 2 (OTX2), can present with a broad range of clinical symptoms, which provides a challenge for predicting phenotype from genotype. Another challenge in human genetics is functional evaluation of rare genetic variants that are predicted to be deleterious. Zebrafish are an excellent vertebrate model for evaluating gene function and disease pathogenesis, especially because large numbers of progeny can be obtained, overcoming the challenge of individual variation. To clarify the utility of zebrafish for the analysis of CPHD-related genes, we analyzed the effect of OTX2 loss of function in zebrafish. The otx2b gene is expressed in the developing hypothalamus, and otx2bhu3625/hu3625 fish exhibit multiple defects in the development of head structures and are not viable past 10 days post fertilization (dpf). Otx2bhu3625/hu3625 fish have a small hypothalamus and low expression of pituitary growth hormone and prolactin (prl). The gills of otx2bhu3625/hu3625 fish have weak sodium influx, consistent with the role of prolactin in osmoregulation. The otx2bhu3625/hu3625 eyes are microphthalmic with colobomas, which may underlie the inability of the mutant fish to find food. The small pituitary and eyes are associated with reduced cell proliferation and increased apoptosis evident at 3 and 5 dpf, respectively. These observations establish the zebrafish as a useful tool for the analysis of CPHD genes with variable and complex phenotypes.

The phenotypic spectrum associated with OTX2 mutations in humans

Objective

The transcription factor OTX2 is implicated in ocular, craniofacial, and pituitary development.

Design

We aimed to establish the contribution of OTX2 mutations in congenital hypopituitarism patients with/without eye abnormalities, study functional consequences, and establish OTX2 expression in the human brain, with a view to investigate the mechanism of action.

Methods

We screened patients from the UK (n = 103), international centres (n = 24), and Brazil (n = 282); 145 were within the septo-optic dysplasia spectrum, and 264 had no eye phenotype. Transactivation ability of OTX2 variants was analysed in murine hypothalamic GT1-7 neurons. In situ hybridization was performed on human embryonic brain sections. Genetically engineered mice were generated with a series of C-terminal OTX2 variants.

Results

Two chromosomal deletions and six haploinsufficient mutations were identified in individuals with eye abnormalities; an affected relative of one patient harboured the same mutation without an ocular phenotype. OTX2 truncations led to significant transactivation reduction. A missense variant was identified in another patient without eye abnormalities; however, studies revealed it was most likely not causative. In the mouse, truncations proximal to aa219 caused anophthalmia, while distal truncations and the missense variant were tolerated. During human embryogenesis, OTX2 was expressed in the posterior pituitary, retina, ear, thalamus, choroid plexus, and partially in the hypothalamus, but not in the anterior pituitary.

Conclusions

OTX2 mutations are rarely associated with hypopituitarism in isolation without eye abnormalities, and may be variably penetrant, even within the same pedigree. Our data suggest that the endocrine phenotypes in patients with OTX2 mutations are of hypothalamic origin.

Hypopituitarism in Patients with Blepharophimosis and FOXL2 Mutations

BACKGROUND

FOXL2 is the gene involved in blepharophimosis, ptosis, and epicanthus inversus syndrome (BPES). There have been few single case reports of growth hormone deficiency (GHD) with this syndrome, and Foxl2 is known to be involved in pituitary development in mice. Our aim was to analyze the prevalence of FOXL2 gene alteration in a series of patients with congenital hypopituitarism and eyelid anomalies.

METHODS

FOXL2 was analyzed in 10 patients with hypopituitarism (ranging from isolated GHD to complete pituitary hormone deficiency) and eyelid anomalies (typical BPES in 4 patients and milder anomalies in 6 patients). In patients with an FOXL2 mutation, we ruled out other possible molecular explanations by analyzing a panel of 20 genes known to be associated with hypopituitarism, and a candidate gene approach was used for patients without an FOXL2mutation.

RESULTS

Three patients had an FOXL2mutation. All 3 had typical BPES. Their pituitary phenotype varied from GHD to complete pituitary hormone deficiency and their pituitary morphology ranged from normal to an interrupted pituitary stalk. No mutations were found in genes previously associated with hypopituitarism.

CONCLUSION

Our study shows that some patients with BPES have hypopituitarism with no molecular explanation other than FOXL2 mutation. This points toward an involvement of FOXL2 in human pituitary development.

Congenital Hypopituitarism During the Neonatal Period: Epidemiology, Pathogenesis, Therapeutic Options, and Outcome

Introduction: Congenital hypopituitarism (CH) is characterized by a deficiency of one or more pituitary hormones. The pituitary gland is a central regulator of growth, metabolism, and reproduction. The anterior pituitary produces and secretes growth hormone (GH), adrenocorticotropic hormone, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. The posterior pituitary hormone secretes antidiuretic hormone and oxytocin. Epidemiology: The incidence is 1 in 4,000-1 in 10,000. The majority of CH cases are sporadic; however, a small number of familial cases have been identified. In the latter, a molecular basis has frequently been identified. Between 80-90% of CH cases remain unsolved in terms of molecular genetics. Pathogenesis: Several transcription factors and signaling molecules are involved in the development of the pituitary gland. Mutations in any of these genes may result in CH including HESX1, PROP1, POU1F1, LHX3, LHX4, SOX2, SOX3, OTX2, PAX6, FGFR1, GLI2, and FGF8. Over the last 5 years, several novel genes have been identified in association with CH, but it is likely that many genes remain to be identified, as the majority of patients with CH do not have an identified mutation. Clinical manifestations: Genotype-phenotype correlations are difficult to establish. There is a high phenotypic variability associated with different genetic mutations. The clinical spectrum includes severe midline developmental disorders, hypopituitarism (in isolation or combined with other congenital abnormalities), and isolated hormone deficiencies. Diagnosis and treatment: Key investigations include MRI and baseline and dynamic pituitary function tests. However, dynamic tests of GH secretion cannot be performed in the neonatal period, and a diagnosis of GH deficiency may be based on auxology, MRI findings, and low growth factor concentrations. Once a hormone deficit is confirmed, hormone replacement should be started. If onset is acute with hypoglycaemia, cortisol deficiency should be excluded, and if identified this should be rapidly treated, as should TSH deficiency. This review aims to give an overview of CH including management of this complex condition.

Pituitary stalk interruption syndrome

Pituitary stalk interruption syndrome (PSIS) is a distinct developmental defect of the pituitary gland identified by magnetic resonance imaging and characterized by a thin, interrupted, attenuated or absent pituitary stalk, hypoplasia or aplasia of the adenohypophysis, and an ectopic posterior pituitary. The precise etiology of PSIS still remains elusive or incompletely confirmed in most cases. Adverse perinatal events, including breech delivery and hypoxia, were initially proposed as the underlying mechanism affecting the hypothalamic-pituitary axis. Nevertheless, recent findings have uncovered a wide variety of PSIS-associated molecular defects in genes involved in pituitary development, holoprosencephaly (HPE), neural development, and other important cellular processes such as cilia function. The application of whole exome sequencing (WES) in relatively large cohorts has identified an expanded pool of potential candidate genes, mostly related to the Wnt, Notch, and sonic hedgehog signaling pathways that regulate pituitary growth and development during embryogenesis. Importantly, WES has revealed coexisting pathogenic variants in a significant number of patients; therefore, pointing to a multigenic origin and inheritance pattern of PSIS. The disorder is characterized by inter- and intrafamilial variability and incomplete or variable penetrance. Overall, PSIS is currently viewed as a mild form of an expanded HPE spectrum. The wide and complex clinical manifestations include evolving pituitary hormone deficiencies (with variable timing of onset and progression) and extrapituitary malformations. Severe and life-threatening symptomatology is observed in a subset of patients with complete pituitary hormone deficiency during the neonatal period. Nevertheless, most patients are referred later in childhood for growth retardation. Prompt and appropriate hormone substitution therapy constitutes the cornerstone of treatment. Further studies are needed to uncover the etiopathogenesis of PSIS.

Congenital pituitary hypoplasia model demonstrates hypothalamic OTX2 regulation of pituitary progenitor cells

Pituitary develops from oral ectoderm in contact with adjacent ventral hypothalamus. Impairment in this process results in congenital pituitary hypoplasia (CPH); however, there have been no human disease models for CPH thus far, prohibiting the elucidation of the underlying mechanisms. In this study, we established a disease model of CPH using patient-derived induced pluripotent stem cells (iPSCs) and 3D organoid technique, in which oral ectoderm and hypothalamus develop simultaneously. Interestingly, patient iPSCs with a heterozygous mutation in the orthodenticle homeobox 2 (OTX2) gene showed increased apoptosis in the pituitary progenitor cells, and the differentiation into pituitary hormone-producing cells was severely impaired. As an underlying mechanism, OTX2 in hypothalamus, not in oral ectoderm, was essential for progenitor cell maintenance by regulating LHX3 expression in oral ectoderm via FGF10 expression in the hypothalamus. Convincingly, the phenotype was reversed by the correction of the mutation, and the haploinsufficiency of OTX2 in control iPSCs revealed a similar phenotype, demonstrating that this mutation was responsible. Thus, we established an iPSC-based congenital pituitary disease model, which recapitulated interaction between hypothalamus and oral ectoderm and demonstrated the essential role of hypothalamic OTX2.

Copy Number Variants Contributing to Combined Pituitary Hormone Deficiency

Combined pituitary hormone deficiency represents a disorder with complex etiology. For many patients, causes of the disease remain unexplained, despite usage of advanced genetic testing. Although major and common transcription factors were identified two decades ago, we still struggle with identification of rare inborn factors contributing to pituitary function. In this report, we follow up genomic screening of CPHD patient cohort that were previously tested for changes in a coding sequences of genes with the use of the whole exome. We aimed to find contribution of rare copy number variations (CNVs). As a result, we identified genomic imbalances in 7 regions among 12 CPHD patients. Five out of seven regions showed copy gains whereas two presented losses of genomic fragment. Three regions with detected gains encompassed known CPHD genes namely LHX4, HESX1, and OTX2. Among new CPHD loci, the most interesting seem to be the region covering SIX3 gene, that is abundantly expressed in developing brain, and together with HESX1 contributes to pituitary organogenesis as it was evidenced before in functional studies. In conclusion, with the use of broadened genomic approach we identified copy number imbalances for 12 CPHD patients. Although further functional studies are required in order to estimate its true impact on expression pattern during pituitary organogenesis and CPHD etiology.

Classification for treatment urgency for the microphthalmia/anophthalmia spectrum using clinical and biometrical characteristics

PURPOSE

Current clinical classifications do not distinguish between the severity of the MICrophthalmia/Anophthalmia (MICA) spectrum with regard to treatment urgency. We aim to provide parameters for distinguishing mild, moderate and severe MICA using clinical and biometrical characteristics.

METHODS

We performed a single-centre, cross-sectional analysis of prospective cohort of 58 MICA children from September 2013 to February 2018 seen at the Amsterdam University Medical Center, The Netherlands. All patients with a visible underdeveloped globe were included. We performed full ophthalmic evaluation including horizontal palpebral fissure length, axial length by ultrasound and/or MRI measurements, paediatric and genetic evaluation. Cases were subdivided based on clinical characteristics. Biometrical data were used to calculate the relative axial length (rAL) and the relative horizontal palpebral fissure length (rHPF) compared with the healthy contralateral eye for unilateral cases.

RESULTS

In previously untreated patients, a strong correlation exists between rAL and rHPF, distinguishing between severe, moderate and mild subjects using rAL of 0-45%, 45-75% and 75%-100%, respectively. Clinical subgroups were randomly dispersed throughout the scatterplot.

CONCLUSION

Current classifications lack clinical implications for MICA patients. We suggest measuring eyelid length and axial length to classify the severity and determine treatment strategy. The 'severe' group has obvious asymmetry and abnormal socket configuration for which therapy should quickly be initiated; the 'moderately' affected group has normal socket anatomy with a microphthalmic eye with disturbing asymmetry for which treatment should be initiated within months of development; the 'mild' group has a slightly smaller axial length or less obvious eyelid asymmetry for which reconstructive correction is possible, but expansive conformer treatment is unnecessary.

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.

Inherited Eye Diseases with Retinal Manifestations through the Eyes of Homeobox Genes

Retinal development is under the coordinated control of overlapping networks of signaling pathways and transcription factors. The paper was conceived as a review of the data and ideas that have been formed to date on homeobox genes mutations that lead to the disruption of eye organogenesis and result in inherited eye/retinal diseases. Many of these diseases are part of the same clinical spectrum and have high genetic heterogeneity with already identified associated genes. We summarize the known key regulators of eye development, with a focus on the homeobox genes associated with monogenic eye diseases showing retinal manifestations. Recent advances in the field of genetics and high-throughput next-generation sequencing technologies, including single-cell transcriptome analysis have allowed for deepening of knowledge of the genetic basis of inherited retinal diseases (IRDs), as well as improve their diagnostics. We highlight some promising avenues of research involving molecular-genetic and cell-technology approaches that can be effective for IRDs therapy. The most promising neuroprotective strategies are aimed at mobilizing the endogenous cellular reserve of the retina.

Septo-optic dysplasia caused by a novel FLNA splice site mutation: a case report

Background

Septo-optic dysplasia (SOD), also known as de-Morsier syndrome, is a rare disorder characterized by any combination of optic nerve hypoplasia, pituitary gland hypoplasia, and midline abnormalities of the brain including absence of the septum pellucidum and corpus callosum dysgenesis. The variable presentation of SOD includes visual, neurologic, and/or hypothalamic-pituitary endocrine defects. The unclear aetiology of a large proportion of SOD cases underscores the importance of identifying novel SOD-associated genes.

Case presentation

To identify the disease-causing gene in a male infant with neonatal hypoglycaemia, dysmorphic features, and hypoplasia of the optic nerve and corpus callosum, we designed a targeted next-generation sequencing panel for brain morphogenesis defects. We identified a novel hemizygous deletion, c.6355 + 4_6355 + 5delAG, in intron 38 of the FLNA gene that the patient had inherited from his mother. cDNA studies showed that this variant results in the production of 3 aberrant FLNA transcripts, the most abundant of which results in retention of intron 38 of FLNA.

Conclusions

We report for the first time a case of early-onset SOD associated with a mutation in the FLNA gene. This finding broadens the spectrum of genetic causes of this rare disorder and expands the phenotypic spectrum of the FLNA gene.

Homozygous variant in OTX2 and possible genetic modifiers identified in a patient with combined pituitary hormone deficiency, ocular involvement, myopathy, ataxia, and mitochondrial impairment

Here we report on a singleton patient affected by a complicated congenital syndrome characterized by growth delay, retinal dystrophy, sensorineural deafness, myopathy, ataxia, combined pituitary hormone deficiency, associated with mitochondrial impairment. Targeted clinical exome sequencing led to the identification of a homozygous missense variant in OTX2. Since only dominant mutations within OTX2 have been associated with cases of syndromic microphthalmia, retinal dystrophy with or without pituitary dysfunctions, this represents the first report of an OTX2 recessive mutation. Part of the phenotype, including ataxia, myopathy and multiple mitochondrial respiratory chain defects, seemed not related to OTX2. Further analysis of next generation sequencing (NGS) data revealed additional candidate variants: a homozygous variant in LETM1, and heterozygous rare variants in AFG3L2 and POLG. All three genes encode mitochondrial proteins and the last two are known to be associated with ataxia, a neurological sign present also in the father of the proband. With our study, we aim to encourage the integration of NGS data with a detailed analysis of clinical description and family history in order to unravel composite genotypes sometimes associated with complicated phenotypes.

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.

Genetics of anophthalmia and microphthalmia. Part 2: Syndromes associated with anophthalmia-microphthalmia

As new genes for A/M are identified in the genomic era, the number of syndromes associated with A/M has greatly expanded. In this review, we provide a brief synopsis of the clinical presentation and molecular genetic etiology of previously characterized pathways involved in A/M, including the Sex-determining region Y-box 2 (SOX2), Orthodenticle Homeobox 2 (OTX2) and Paired box protein-6 (PAX6) genes, and the Stimulated by retinoic acid gene 6 homolog (STRA6), Aldehyde Dehydrogenase 1 Family Member A3 (ALDH1A3), and RA Receptor Beta (RARβ) genes that are involved in retinoic acid synthesis. Less common genetic causes of A/M, including genes involved in BMP signaling [Bone Morphogenetic Protein 4 (BMP4), Bone Morphogenetic Protein 7 (BMP7) and SPARC-related modular calcium-binding protein 1 (SMOC1)], genes involved in the mitochondrial respiratory chain complex [Holocytochrome c-type synthase (HCCS), Cytochrome C Oxidase Subunit 7B (COX7B), and NADH:Ubiquinone Oxidoreductase subunit B11 (NDUFB11)], the BCL-6 corepressor gene (BCOR), Yes-Associated Protein 1 (YAP1) and Transcription Factor AP-2 Alpha (TFAP2α), are more briefly discussed. We also review several recently described genes and pathways associated with A/M, including Smoothened (SMO) that is involved in Sonic hedgehog (SHH) signaling, Structural maintenance of chromosomes flexible hinge domain containing 1 (SMCHD1) and Solute carrier family 25 member 24 (SLC25A24), emphasizing phenotype-genotype correlations and shared pathways where relevant.

New insights into the phenotypic spectrum of 14q22q23 deletions: a case report and literature review

BACKGROUND

Mutations occurring in the orthodenticle homeobox 2 gene (OTX2) are responsible for a rare genetic syndrome, characterized mainly by microphthalmia/anophthalmia associated with extra-ocular defects such as brain malformations, pituitary abnormalities, short stature and intellectual disability. To date, the spectrum of radiological features observed in patients with OTX2 mutations has never been summarized.

CASE PRESENTATION

In this report, we describe a case of large microdeletion encompassing OTX2 but not BMP4 presenting with a syndromic anophthalmia with corpus callosum hypoplasia, pituitary gland hypoplasia and vermian hypoplasia.

CONCLUSION

Our case report provides an illustration of the neuroradiological spectrum in a case of OTX2-related syndrome and the first radiological evidence of 14q22.2q23.1 deletion associated posterior cranial fossa anomalies.

Haploinsufficiency of Homeodomain Proteins Six3, Vax1, and Otx2 Causes Subfertility in Mice via Distinct Mechanisms

Haploinsufficiency occurs when loss of one copy of a diploid gene (hemizygosity) causes a phenotype. It is relatively rare, in that most genes can produce sufficient mRNA and protein from a single copy to prevent any loss of normal activity and function. Reproduction is a complex process relying on migration of GnRH neurons from the olfactory placode to the hypothalamus during development. We have studied 3 different homeodomain genes Otx2, Vax1, and Six3 and found that the deletion of one allele for any of these genes in mice produces subfertility or infertility in one or both sexes, despite the presence of one intact allele. All 3 heterozygous mice have reduced numbers of GnRH neurons, but the mechanisms of subfertility differ significantly. This review compares the subfertility phenotypes and their mechanisms.

Tolvaptan for Primary Aldosteronism and Autosomal Dominant Polycystic Kidney Disease: A Case Report

A 59-year-old Japanese woman was admitted for evaluation of muscle weakness. Autosomal dominant polycystic kidney disease had been diagnosed at the age of 47 years, followed by primary aldosteronism at 53 years. At the age of 58, tolvaptan was started (60 mg/day) to treat her renal disease. After 8 months of tolvaptan therapy, hypokalemia-related muscle weakness became prominent, and hypertension became refractory. Finally, treatment with low-dose tolvaptan (30 mg/day) and high-dose spironolactone (100 mg/day) normalized serum potassium and the blood pressure. Tolvaptan can induce urinary excretion of potassium in patients with primary aldosteronism, and possible mechanisms are discussed.

Transcriptional interaction between cFOS and the homeodomain-binding transcription factor VAX1 on the GnRH promoter controls Gnrh1 expression levels in a GnRH neuron maturation specific manner

Gonadotropin-releasing hormone (GnRH) is required for pubertal onset and reproduction, thus the control of GnRH transcription is tightly regulated during development and adulthood. GnRH neuron development depends on transcription factors of the homeodomain family. For example, Ventral anterior homeobox 1 (Vax1) is necessary to maintain GnRH expression after embryonic day 13 in the mouse. To further our understanding of the mechanisms by which VAX1 regulates GnRH gene expression, we asked whether VAX1 interacts with other transcription factors to modify GnRH expression levels. Using the GnRH cell lines, GN11 and GT1-7, we found that activation of PKC enhances expression of the immediate early gene cFos in both GN11, and GT1-7, and represses expression of Vax1 in GT1-7. Further, VAX1 interacts with cFOS while bound to the GnRH promoter. In immature GN11 cells, VAX1 and cFOS enhance GnRH expression, whereas VAX1 and cFOS have a repressive role in the mature GT1-7 cells.

Prescreening whole exome sequencing results from patients with retinal degeneration for variants in genes associated with retinal degeneration

Background

Accurate clinical diagnosis and prognosis of retinal degeneration can be aided by the identification of the disease-causing genetic variant. It can confirm the clinical diagnosis as well as inform the clinician of the risk for potential involvement of other organs such as kidneys. It also aids in genetic counseling for affected individuals who want to have a child. Finally, knowledge of disease-causing variants informs laboratory investigators involved in translational research. With the advent of next-generation sequencing, identifying pathogenic mutations is becoming easier, especially the identification of novel pathogenic variants.

Methods

We used whole exome sequencing on a cohort of 69 patients with various forms of retinal degeneration and in whom screens for previously identified disease-causing variants had been inconclusive. All potential pathogenic variants were verified by Sanger sequencing and, when possible, segregation analysis of immediate relatives. Potential variants were identified by using a semi-masked approach in which rare variants in candidate genes were identified without knowledge of the clinical diagnosis (beyond "retinal degeneration") or inheritance pattern. After the initial list of genes was prioritized, genetic diagnosis and inheritance pattern were taken into account.

Results

We identified the likely pathogenic variants in 64% of the subjects. Seven percent had a single heterozygous mutation identified that would cause recessive disease and 13% had no obviously pathogenic variants and no family members available to perform segregation analysis. Eleven subjects are good candidates for novel gene discovery. Two de novo mutations were identified that resulted in dominant retinal degeneration.

Conclusion

Whole exome sequencing allows for thorough genetic analysis of candidate genes as well as novel gene discovery. It allows for an unbiased analysis of genetic variants to reduce the chance that the pathogenic mutation will be missed due to incomplete or inaccurate family history or analysis at the early stage of a syndromic form of retinal degeneration.

Multi-genic pattern found in rare type of hypopituitarism: a whole-exome sequencing study of Han Chinese with pituitary stalk interruption syndrome

Pituitary stalk interruption syndrome (PSIS) is a rare type of hypopituitarism manifesting various degrees of pituitary hormone deficiency. Although mutations have been identified in some familial cases, the underpinning mechanisms of sporadic patients with PSIS who are in a vast majority remain elusive, necessitating a comprehensive study using systemic approaches. We postulate that other genetic mechanisms may be responsible for the sporadic PSIS. To test this hypothesis, we conducted a study in 24 patients with PSIS of Han Chinese with no family history using whole‐exome sequencing (WES) and bioinformatic analysis. We identified a group of heterozygous mutations in 92% (22 of 24) of the patients, and these genes are mostly associated with Notch, Shh, Wnt signalling pathways. Importantly, 83% (20 of 24) of the patients had more than one mutation in those pathways suggesting synergy of compound mutations underpin the pathogenesis of sporadic PSIS.

Pituitary Hypoplasia

This article summarizes pituitary development and function as well as specific mutations of genes encoding the following transcription factors: HESX1, LHX3, LHX4, POU1F1, PROP1, and OTX2. Although several additional genetic defects related to hypopituitarism have been identified, this article focuses on these selected factors, as they have been well described in the literature in terms of clinical characterization of affected patients and molecular mechanisms of action, and therefore, are very relevant to clinical practice.

A Novel Mutation in OTX2 Causes Combined Pituitary Hormone Deficiency, Bilateral Microphthalmia, and Agenesis of the Left Internal Carotid Artery

BACKGROUND

Mutations in OTX2 cause hypopituitarism, ranging from isolated growth hormone deficiency to combined pituitary hormone deficiency (CPHD), which are commonly detected in association with severe eye abnormalities, including anophthalmia or microphthalmia. Pituitary phenotypes of OTX2 mutation carriers are highly variable; however, ACTH deficiency during the neonatal period is not common in previous reports.

OBJECTIVE

We report a novel missense OTX2 (R89P) mutation in a CPHD patient with severe hypoglycemia in the neonatal period due to ACTH deficiency, bilateral microphthalmia, and agenesis of the left internal carotid artery (ICA).

RESULTS

We identified a novel heterozygous mutation in OTX2 (c.266G>C, p.R89P). R89P OTX2 showed markedly reduced transcriptional activity of HESX1 and POU1F1 reporters compared with wild-type OTX2. A dominant negative effect was noted only in the transcription analysis with POU1F1 promoter. Electrophoretic mobility shift assay experiments showed that R89P OTX2 abrogated DNA-binding ability.

CONCLUSION

OTX2 mutations can cause ACTH deficiency in the neonatal period. Our study also shows that OTX2 mutations are associated with agenesis of the ICA. To the best of our knowledge, this is the first report of a transcription factor gene mutation, which was identified due to agenesis of the ICA of a patient with CPHD. This study extends our understanding of the phenotypic features, molecular mechanism, and developmental course associated with mutations in OTX2.

Characterization of a novel HESX1 mutation in a pediatric case of septo-optic dysplasia

Septo‐optic dysplasia (SOD) is a rare condition for which the precise etiology is still unclear. Elucidating the genetic component of SOD is a difficult but necessary task for the future. We describe herein a novel HESX1 c.475C>T (p.R159W) mutation and demonstrate its potential pathogenicity in the development of this rare disease.

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.

Mandibular dysostosis without microphthalmia caused by OTX2 deletion

Mutations in OTX2 are mostly identified in patients with anophthalmia/microphthalmia with variable severity. The OTX2 homeobox gene plays a crucial role in craniofacial morphogenesis during early embryo development. We report for the first time a patient with a mandibular dysostosis caused by a 120 kb deletion including the entire coding sequence of OTX2, identified by array CGH. No ocular malformations were identified after extended ophthalmologic examination. Our data refine the clinical spectrum associated with OTX2 mutations and suggests that OTX2 haploinsufficiency should be considered as a possible cause for isolated mandibular dysostosis. © 2016 Wiley Periodicals, Inc.

A novel OTX2 gene frameshift mutation in a child with microphthalmia, ectopic pituitary and growth hormone deficiency

OTX2 mutations are reported in patients with eye maldevelopment and in some cases with brain or pituitary abnormalities. We describe a child carrying a novel OTX2 heterozygous mutation. She presented microphthalmia, absence of retinal vascularization, vitreal spots and optic nerve hypoplasia in the right eye and mild macular dystrophy in the left eye. Midline brain structures and cerebral parenchyma were normal, except for the ectopic posterior pituitary gland. OTX2 sequencing showed a heterozygous c.402del mutation. Most of OTX2 mutations are nonsense or frameshift introducing a premature termination codon and resulting in a truncated protein. More rarely missense mutations occur. Our novel OTX2 mutation (c.402del) is a frameshift mutation (p.S135Lfs*43), never reported before, causing a premature codon stop 43 amino-acids downstream, which is predicted to generate a premature truncation. The mutation was associated with microphthalmia and ectopic posterior pituitary.

Kisspeptin Induces Dynamic Chromatin Modifications to Control GnRH Gene Expression

In vitro studies have demonstrated an increase in GnRH gene expression associated with an elevated secretory response to kisspeptin administration, suggesting that kisspeptin mediates GnRH expression at both the secretory and pretranslational levels. However, the kisspeptin-mediated intracellular mechanisms associated with the dynamic chromatin modifications modulating GnRH gene expression are unclear. The studies in this manuscript describe specific histone modifications on the enhancer and promoter of the mouse GnRH (mGnRH) gene induced by kisspeptin in GnRH neuronal cell lines (GT1-7 cells). ChIP assays followed by quantitative real-time PCR (qPCR) demonstrate that 15 and 45 min of 10(-9) M kisspeptin significantly increased histone 3 acetylation (H3Ac) at the kisspeptin response element (KsRE) contained between -3446 and -2806 bp of the mGnRH enhancer (GnRHen) in GT1-7 cells, while no changes were observed in the downstream neuron-specific element (NSE). Moreover, kisspeptin specifically induced acetylation of H3AcK14 and K27 and trimethylation of H3 lysine 4 at the KsRE (markers of active chromatin) and no changes in dimethylation of H3K9 (a marker associated with gene repression). Occupancy of RNA Pol II (RNAPII) and a differential carboxyl-terminal domain (CTD) phosphorylation pattern was observed. An interaction between the NSE and the KsRE via a chromatin loop in the mGnRH gene by kisspeptin was detected by the chromosome conformation capture assay (3C). In conclusion, these results demonstrate that kisspeptin induces histone acetylation/methylation and consequently enhances the formation of a chromatin loop in the mGnRH gene which results in known increase in kisspeptin-dependent mGnRH expression.

Role of GLI2 in hypopituitarism phenotype

GLI2 is a zinc-finger transcription factor involved in the Sonic Hedgehog pathway. Gli2 mutant mice have hypoplastic anterior and absent posterior pituitary glands. We reviewed the literature for patients with hypopituitarism and alterations in GLI2. Twenty-five patients (16 families) had heterozygous truncating mutations, and the phenotype frequently included GH deficiency, a small anterior pituitary lobe and an ectopic/undescended posterior pituitary lobe on magnetic resonance imaging and postaxial polydactyly. The inheritance pattern was autosomal dominant with incomplete penetrance and variable expressivity. The mutation was frequently inherited from an asymptomatic parent. Eleven patients had heterozygous non-synonymous GLI2 variants that were classified as variants of unknown significance, because they were either absent from or had a frequency lower than 0.001 in the databases. In these patients, the posterior pituitary was also ectopic, but none had polydactyly. A third group of variants found in patients with hypopituitarism were considered benign because their frequency was ≥ 0.001 in the databases. GLI2 is a large and polymorphic gene, and sequencing may identify variants whose interpretation may be difficult. Incomplete penetrance implies in the participation of other genetic and/or environmental factors. An interaction between Gli2 mutations and prenatal ethanol exposure has been demonstrated in mice dysmorphology. In conclusion, a relatively high frequency of GLI2 mutations and variants were identified in patients with congenital GH deficiency without other brain defects, and most of these patients presented with combined pituitary hormone deficiency and an ectopic posterior pituitary lobe. Future studies may clarify the relative role and frequency of GLI2 alterations in the aetiology of hypopituitarism.

Combined pituitary hormone deficiency: current and future status

Over the last two decades, the understanding of the mechanisms involved in pituitary ontogenesis has largely increased. Since the first description of POU1F1 human mutations responsible for a well-defined phenotype without extra-pituitary malformation, several other genetic defects of transcription factors have been reported with variable degrees of phenotype-genotype correlations. However, to date, despite the identification of an increased number of genetic causes of isolated or multiple pituitary deficiencies, the etiology of most (80-90 %) congenital cases of hypopituitarism remains unsolved. Identifying new etiologies is of importance as a post-natal diagnosis to better diagnose and treat the patients (delayed pituitary deficiencies, differential diagnosis of a pituitary mass on MRI, etc.), and as a prenatal diagnosis to decrease the risk of early death (undiagnosed corticotroph deficiency for instance). The aim of this review is to summarize the main etiologies and phenotypes of combined pituitary hormone deficiencies, associated or not with extra-pituitary anomalies, and to suggest how the identification of such etiologies could be improved in the near future.

Deletion of OTX2 in neural ectoderm delays anterior pituitary development

OTX2 is a homeodomain transcription factor that is necessary for normal head development in mouse and man. Heterozygosity for loss-of-function alleles causes an incompletely penetrant, haploinsufficiency disorder. Affected individuals exhibit a spectrum of features that range from developmental defects in eye and/or pituitary development to acephaly. To investigate the mechanism underlying the pituitary defects, we used different cre lines to inactivate Otx2 in early head development and in the prospective anterior and posterior lobes. Mice homozygous for Otx2 deficiency in early head development and pituitary oral ectoderm exhibit craniofacial defects and pituitary gland dysmorphology, but normal pituitary cell specification. The morphological defects mimic those observed in humans and mice with OTX2 heterozygous mutations. Mice homozygous for Otx2 deficiency in the pituitary neural ectoderm exhibited altered patterning of gene expression and ablation of FGF signaling. The posterior pituitary lobe and stalk, which normally arise from neural ectoderm, were extremely hypoplastic. Otx2 expression was intact in Rathke's pouch, the precursor to the anterior lobe, but the anterior lobe was hypoplastic. The lack of FGF signaling from the neural ectoderm was sufficient to impair anterior lobe growth, but not the differentiation of hormone-producing cells. This study demonstrates that Otx2 expression in the neural ectoderm is important intrinsically for the development of the posterior lobe and pituitary stalk, and it has significant extrinsic effects on anterior pituitary growth. Otx2 expression early in head development is important for establishing normal craniofacial features including development of the brain, eyes and pituitary gland.

OTX2 mutations cause autosomal dominant pattern dystrophy of the retinal pigment epithelium

PURPOSE

To identify the genetic cause of autosomal-dominant pattern dystrophy (PD) of the retinal pigment epithelium (RPE) in two families.

METHODS AND RESULTS

Two families with autosomal-dominant PD were identified. Eight members of family 1 (five affected) were subjected to whole-genome SNP genotyping; multipoint genome-wide linkage analysis identified 7 regions of potential linkage, and genotyping four additional individuals from family 1 resulted in a maximum logarithm of odds score of 2.09 observed across four chromosomal regions. Exome sequencing of two affected family 1 members identified 15 shared non-synonymous rare coding sequence variants within the linked regions; candidate genes were prioritised and further analysed. Sanger sequencing confirmed a novel heterozygous missense variant (E79K) in orthodenticle homeobox 2 (OTX2) that segregated with the disease phenotype. Family 2 with PD (two affected) harboured the same missense variant in OTX2. A shared haplotype of 19.68 cM encompassing OTX2 was identified between affected individuals in the two families. Within the two families, all except one affected demonstrated distinct 'patterns' at the macula. In vivo structural retinal imaging showed discrete areas of RPE-photoreceptor separation at the macula in all cases. Electroretinogram testing showed generalised photoreceptor degeneration in three cases. Mild developmental anomalies were observed, including optic nerve head dysplasia (four cases), microcornea (one case) and Rathke's cleft cyst (one case); pituitary hormone levels were normal.

CONCLUSIONS

This is the first report implicating OTX2 to underlie PD. The retinal disease resembles conditional mice models that show slow photoreceptor degeneration secondary to loss of Otx2 function in the adult RPE.

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.

The genetic architecture of microphthalmia, anophthalmia and coloboma

Microphthalmia, anophthalmia and coloboma (MAC) are distinct phenotypes that represent a continuum of structural developmental eye defects. In severe bilateral cases (anophthalmia or severe microphthalmia) the genetic cause is now identifiable in approximately 80 percent of cases, with de novo heterozygous loss-of-function mutations in SOX2 or OTX2 being the most common. The genetic cause of other forms of MAC, in particular isolated coloboma, remains unknown in the majority of cases. This review will focus on MAC phenotypes that are associated with mutation of the genes SOX2, OTX2, PAX6, STRA6, ALDH1A3, RARB, VSX2, RAX, FOXE3, BMP4, BMP7, GDF3, GDF6, ABCB6, ATOH7, C12orf57, TENM3 (ODZ3), and VAX1. Recently reported mutation of the SALL2 and YAP1 genes are discussed in brief. Clinical and genetic features were reviewed in a total of 283 unrelated MAC cases or families that were mutation-positive from these 20 genes. Both the relative frequency of mutations in MAC cohort screens and the level of confidence in the assignment of disease-causing status were evaluated for each gene.

Anophthalmia, hearing loss, abnormal pituitary development and response to growth hormone therapy in three children with microdeletions of 14q22q23

BACKGROUND

Microdeletions of 14q22q23 have been associated with eye abnormalities and pituitary defects. Other phenotypic features in deletion carriers including hearing loss and response to growth hormone therapy are less well recognized. We studied genotype and phenotype of three newly identified children with 14q22q23 deletions, two girls and one boy with bilateral anophthalmia, and compared them with previously published deletion patients and individuals with intragenic defects in genes residing in the region.

RESULTS

The three deletions were de novo and ranged in size between 5.8 and 8.9 Mb. All three children lacked one copy of the OTX2 gene and in one of them the deletion involved also the BMP4 gene. All three patients presented partial conductive hearing loss which tended to improve with age. Analysis of endocrine and growth phenotypes showed undetectable anterior pituitary, growth hormone deficiency and progressive growth retardation in all three patients. Growth hormone therapy led to partial catch-up growth in two of the three patients but just prevented further height loss in the third.

CONCLUSIONS

The pituitary hypoplasia, growth hormone deficiency and growth retardation associated with 14q22q23 microdeletions are very remarkable, and the latter appears to have an atypical response to growth hormone therapy in some of the cases.

Gene dosage of Otx2 is important for fertility in male mice

Together, the hypothalamus, pituitary and gonads direct the development and regulation of reproductive function in mammals. Gonadotropin-releasing hormone (GnRH) expression is limited to ∼800 neurons that originate in the olfactory placode then migrate to the hypothalamus. Coordination of the hypothalamic-pituitary-gonadal (HPG) axis is dependent upon correct neuronal migration of GnRH neurons into the hypothalamus followed by proper synthesis and pulsatile secretion of GnRH. Defects in any one of these processes causes infertility. Otx2, the vertebrate homologue of Drosophila orthodenticle, is a transcription factor that has been shown to be critical for normal brain and eye development and is expressed in both the developing GnRH neurons and the pituitary, suggesting that this gene may play a critical role in development of the HPG axis. As Otx2-null mice are embryonic lethal, we have analyzed the reproductive capacity of heterozygous Otx2 mice to determine the contribution of Otx2 gene dosage to normal HPG axis function. Our data reveal that correct dosage of Otx2 is critical for normal fertility as loss of one allele of Otx2 leads to a discernible reproductive phenotype in male mice due to disruption of the migration of GnRH neurons during development.

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.

Molecular and Clinical Findings in Patients with LHX4 and OTX2 Mutations

The pituitary gland produces hormones that play important roles in both the development and homeostasis of the body. Ontogeny of the anterior and posterior pituitary is orchestrated by inputs from neighboring tissues, cellular signaling molecules and transcription factors. Disruption of expression or function of these factors has been implicated in the etiology of combined pituitary hormone deficiency (CPHD). These include the transcription factors HESX1, PROP1, POU1F1, LHX3, LHX4, OTX2, SOX2, SOX3 and GLI2. This review focuses on summarizing most recent mutations in LHX4 and OTX2 responsible for pituitary hormone deficiency. In both genetic defects of LHX4 and OTX2, there is high variability in clinical manifestations even in the same family. In addition, there is no clear phenotype-genotype correlation. These findings indicate that the other genetic and/or environmental factors influence the phenotype. In addition, the variability might reflect a plasticity during pituitary development and maintenance. Over the past two decades, a genetic basis for pituitary hormone deficiency and the mechanism of pituitary development have been clarified. It should be kept in mind that this review is not comprehensive, and defects of other transcriptional factors have been described in patients with CPHD. Furthermore, the causes in many patients with CPHD have not yet been determined. Therefore, continuing efforts for the clarification of the etiology are necessary.

Molecular and Clinical Findings in Patients with LHX4 and OTX2 Mutations

The pituitary gland produces hormones that play important roles in both the development and homeostasis of the body. Ontogeny of the anterior and posterior pituitary is orchestrated by inputs from neighboring tissues, cellular signaling molecules and transcription factors. Disruption of expression or function of these factors has been implicated in the etiology of combined pituitary hormone deficiency (CPHD). These include the transcription factors HESX1, PROP1, POU1F1, LHX3, LHX4, OTX2, SOX2, SOX3 and GLI2. This review focuses on summarizing most recent mutations in LHX4 and OTX2 responsible for pituitary hormone deficiency. In both genetic defects of LHX4 and OTX2, there is high variability in clinical manifestations even in the same family. In addition, there is no clear phenotype-genotype correlation. These findings indicate that the other genetic and/or environmental factors influence the phenotype. In addition, the variability might reflect a plasticity during pituitary development and maintenance. Over the past two decades, a genetic basis for pituitary hormone deficiency and the mechanism of pituitary development have been clarified. It should be kept in mind that this review is not comprehensive, and defects of other transcriptional factors have been described in patients with CPHD. Furthermore, the causes in many patients with CPHD have not yet been determined. Therefore, continuing efforts for the clarification of the etiology are necessary.

Specific expression pattern of a novel Otx2 splicing variant during neural differentiation

We cloned a new splicing variant of Otx2 gene, Otx2c. Otx2c lacks entire exon 4, most of the region encoding the homeodomain. More importantly, Otx2c harbors an early premature stop codon and bioinformatics analysis prefers it to be a non-protein coding RNA. In addition, this splicing variant is not simply a noise during mRNA processing, since it is mainly expressed in undifferentiated human embryonic stem cells but gradually decreased during differentiation. Therefore, we report here that a single pre-mRNA can generate both coding and non-coding RNAs through alternative splicing and this splicing activity is tightly regulated in different cell contexts.

Relatively high frequency of non-synonymous GLI2 variants in patients with congenital hypopituitarism without holoprosencephaly

OBJECTIVE

GLI2 is a downstream transcription factor in Sonic Hedgehog signalling, acting early in ventral forebrain and pituitary development. Heterozygous nonsense GLI2 mutations have been reported in patients with isolated or combined pituitary hormone deficiency (CPHD), with or without holoprosencephaly. The aim of this study was to screen for GLI2 mutations in a large cohort of patients with congenital GH deficiency.

DESIGN AND PATIENTS

The GLI2 coding region of 41 patients with severe isolated GH deficiency (IGHD) and 136 patients with CPHD was amplified by PCR using intronic primers and sequenced. The frequency of GLI2 variants was verified in up to 155 Brazilian controls and in the 1000 Genomes database. The consequences of allelic variants were analysed by the Polyphen, SIFT, Mutationtaster and SNAP prediction sites.

RESULTS

Eighteen different heterozygous non-synonymous GLI2 variants were identified in 24 patients. Twenty-three patients had CPHD and one had IGHD. Two patients had additional diabetes insipidus, indicating deficiencies of anterior and posterior pituitary lobes. The posterior pituitary lobe on MRI was ectopic in 16, not visible in 4, normally placed in 2 and imaging was not available in two patients, but there were no signs of holoprosencephaly. Sixteen GLI2 variants were considered deleterious in at least one of the prediction sites.

CONCLUSIONS

A relatively high frequency of non-synonymous GLI2 variants was identified in patients with congenital GH deficiency without other brain defects, and most of these patients presented with CPHD and an ectopic posterior pituitary lobe. In vitro functional assays may contribute to ascertain the deleterious consequences of these variants.

Clinical and mutation analysis of 51 probands with anophthalmia and/or severe microphthalmia from a single center

Clinical evaluation and mutation analysis was performed in 51 consecutive probands with severe eye malformations - anophthalmia and/or severe microphthalmia - seen in a single specialist ophthalmology center. The mutation analysis consisted of bidirectional sequencing of the coding regions of SOX2, OTX2, PAX6 (paired domain), STRA6, BMP4, SMOC1, FOXE3, and RAX, and genome-wide array-based copy number assessment. Fifteen (29.4%) of the 51 probands had likely causative mutations affecting SOX2 (9/51), OTX2 (5/51), and STRA6 (1/51). Of the cases with bilateral anophthalmia, 9/12 (75%) were found to be mutation positive. Three of these mutations were large genomic deletions encompassing SOX2 (one case) or OTX2 (two cases). Familial inheritance of three intragenic, plausibly pathogenic, and heterozygous mutations was observed. An unaffected carrier parent of an affected child with an identified OTX2 mutation confirmed the previously reported nonpenetrance for this disorder. Two families with SOX2 mutations demonstrated a parent and child both with significant but highly variable eye malformations. Heterozygous loss-of-function mutations in SOX2 and OTX2 are the most common genetic pathology associated with severe eye malformations and bi-allelic loss-of-function in STRA6 is confirmed as an emerging cause of nonsyndromal eye malformations.