Mutation and gene copy number analyses of six pituitary transcription factor genes in 71 patients with combined pituitary hormone deficiency: identification of a single patient with LHX4 deletion

Comparison of clinical characteristics of a pediatric cohort with combined pituitary hormone deficiency caused by mutation of the PROP1 gene or of other origins

The most commonly identified genetic cause of combined pituitary hormone deficiency (CPHD) is PROP1 gene mutations. The aim of the study was to compare selected clinical features of patients with CPHD caused by variants of the PROP1 gene (CPHD-PROP1) and patients with inborn CPHD of other etiology (CPHD-nonPROP1).

MATERIAL AND METHODS

The retrospective analysis included childhood medical records of 74 patients (32 female) with CPHD, including 43 patients (23 female) with the mutation in the PROP1 gene.

RESULTS

Patients with CPHD-PROP1 compared to the CPHD-nonPROP1 presented with the following: significantly higher median birth weight (0.21 vs. - 0.29 SDS, p = 0.019), lower growth velocity within 3 years preceding growth hormone administration (- 2.7 vs. - 0.8 SDS, p < 0.001), higher mean maximal blood concentration of growth hormone within the stimulation process (1.2 vs. 1.08 ng/mL, p = 0.003), lower TSH (1.8 vs. 2.4 µIU/mL, p < 0.001), significantly lower prolactin concentrations (128 vs. 416.3 µIU/mL, p < 0.001), and less frequent typical signs of hypogonadism at birth in boys (n = 6; 30% vs. n = 12, 54%, p < 0.001). Secondary adrenal insufficiency was less frequent in CPHD-PROP1 (20 vs. 25 cases, p = 0.006) and occurred at a later age (13.4 vs. 10.4 years). MRI of the pituitary gland in CPHD-PROP1 revealed a small pituitary gland (21 cases), pituitary gland enlargement (eight cases), and one pituitary stalk interruption and posterior lobe ectopy, while it was normal in nine cases.

CONCLUSION

Patients with the PROP1 mutations present a clinical picture significantly different from that of other forms of congenital hypopituitarism. Certain specific clinical results may lead to the successful identification of children requiring diagnostics for the PROP1 gene mutation.

Normal or elevated prolactin is a good indicator to show pituitary stalk interruption syndrome in patients with multiple pituitary hormone deficiency

OBJECTIVES

To determine the importance of serum prolactin (PRL) in the detection of pituitary stalk interruption syndrome (PSIS) in children with multiple pituitary hormone deficiency (MPHD). We hypothesized that PRL elevation might be a diagnostic indicator of pituitary stalk pathologies.

METHODS

Clinical, radiological, and laboratory features of the 50 cases of MPHD were studied.

RESULTS

The median age at presentation of the 50 cases (52%, n=26 were female) was 6.61 (0.02-18.9) years. PSIS was detected in 60% (n=30), pituitary hypoplasia in 32% (n=16), partial empty sella in 6% (n=3), and only 2% (n=1) was reported as normal. Out of 50 patients, 21.3% (n=10) were hypoprolactinemic, 44.7% (n=19) were normoprolactinemic, and 34% (n=16) were hyperprolactinemic. The median PRL value was 27.85 (4.21-130) ng/mL in patients with PSIS and 5.57 (0-41.8) ng/mL in patients without PSIS. Additional hormone deficiencies, especially ACTH and LH were detected in follow-up.

CONCLUSIONS

Patients with normal or high prolactin levels deserve special attention regarding the possibility of PSIS. Furthermore, we emphasize the importance of regular follow-up and monitoring for multiple pituitary hormone deficiencies in all patients with a single pituitary hormone deficiency.

Hemiparesis With Hypoglycemia in a Child With Hypopituitarism Involving LHX4 Gene Deletion

We report a case of a 17-month-old boy with developmental delay who presented with acute-onset right-sided hemiparesis and hypoglycemia. Severe hypotension developed during his sedation for MRI and magnetic resonance angiography. Imaging revealed a hypoplastic pituitary gland within a shallow sella turcica and findings suggestive of moyamoya syndrome. Hemiparesis resolved 5 hours after correction of hypoglycemia with dextrose infusion, and severe hypotension improved with crystalloid fluids and vasopressors. Magnetic resonance angiography repeated 24 hours later revealed resolution of the vascular finding. Additional biochemical testing was consistent with hypopituitarism, and genetic evaluation revealed that the patient had a microdeletion including the LHX4 gene, which has been implicated in combined pituitary hormone deficiency type IV. Hypoglycemia frequently presents with autonomic or neuroglycopenic symptoms. However, when hypoglycemia presents with an isolated neurologic deficit like hemiparesis with preservation of alertness, it can be challenging to differentiate a cerebrovascular event from hypoglycemia-induced symptoms, leading to a delay in endocrine evaluation. Hypoglycemic hemiparesis is rare in childhood and is reported in children with diabetes mellitus or hyperinsulinism. This case expands the clinical spectrum of hemiparesis as a presenting sign of hypoglycemia in growth hormone and adrenocorticotropic hormone/cortisol deficiencies.

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.

Clinical lessons learned in constitutional hypopituitarism from two decades of experience in a large international cohort

CONTEXT

The international GENHYPOPIT network collects phenotypical data and screens genetic causes of non-acquired hypopituitarism.

AIMS

To describe main phenotype patterns and their evolution through life.

DESIGN

Patients were screened according to their phenotype for coding sequence variations in 8 genes: HESX1, LHX3, LHX4, PROP1, POU1F1, TBX19, OTX2 and PROKR2.

RESULTS

Among 1213 patients (1143 index cases), the age of diagnosis of hypopituitarism was congenital (24%), in childhood (28%), at puberty (32%), in adulthood (7.2%) or not available (8.8%). Noteworthy, pituitary hormonal deficiencies kept on evolving during adulthood in 49 of patients. Growth Hormone deficiency (GHD) affected 85.8% of patients and was often the first diagnosed deficiency. AdrenoCorticoTropic Hormone deficiency rarely preceded GHD, but usually followed it by over 10 years. Pituitary Magnetic Resonance Imaging (MRI) abnormalities were common (79.7%), with 39.4% pituitary stalk interruption syndrome (PSIS). The most frequently associated extrapituitary malformations were ophthalmological abnormalities (16.1%). Prevalence of identified mutations was 7.3% of index cases (84/1143) and 29.5% in familial cases (n = 146). Genetic analysis in 449 patients without extrapituitary phenotype revealed 36 PROP1, 2 POU1F1 and 17 TBX19 mutations.

CONCLUSION

This large international cohort highlights atypical phenotypic presentation of constitutional hypopituitarism, such as post pubertal presentation or adult progression of hormonal deficiencies. These results justify long-term follow-up, and the need for systematic evaluation of associated abnormalities. Genetic defects were rarely identified, mainly PROP1 mutations in pure endocrine phenotypes.

LIM Homeobox 4 (lhx4) regulates retinal neural differentiation and visual function in zebrafish

LIM homeobox 4 (LHX4) is expressed in the photoreceptors (PRs) of the outer nuclear layer (ONL) and bipolar cells (BCs) of the inner nuclear layer (INL) in mouse and chicken retina. It regulates the subtype-specific development of rod BCs and cone BCs in the mouse retina. However, no report has been published on its expression and function in the zebrafish retina. In this study, we assessed the expression of Lhx4 using in situ hybridization (ISH) technique and explored its role in zebrafish (Danio rerio) retinal development via morpholino (MO) technology. We found that the expression of lhx4 in the zebrafish retina begins 48 h post-fertilization (hpf) and is continuously expressed in the ONL and INL. A zebrafish model constructed with lhx4 knockdown in the eyes through vivo-MO revealed that: lhx4 knockdown inhibits the differentiation of Parvalbumin⁺ amacrine cells (ACs) and Rhodopsin⁺ rod photoreceptors (RPs), enhances the expression of visual system homeobox 2 (vsx2); and damages the responses of zebrafish to light stimulus, without affecting the differentiation of OFF-BCs and rod BCs, and apoptosis in the retina. These findings reveal that lhx4 regulates neural differentiation in the retina and visual function during zebrafish embryonic development.

Genetic spectrum and predictors of mutations in four known genes in Asian Indian patients with growth hormone deficiency and orthotopic posterior pituitary: an emphasis on regional genetic diversity

CONTEXT

Regional variation in prevalence of genetic mutations in growth hormone deficiency (GHD) is known.

AIM

Study phenotype and prevalence of mutations in GH1, GHRHR, POU1F1, PROP1 genes in GHD cohort.

METHODS

One hundred and two patients {Isolated GHD (IGHD): 79; combined pituitary hormone deficiency (CPHD): 23} with orthotopic posterior pituitary were included. Auxologic, hormonal and radiological details were studied. All four genes were analysed in IGHD patients. POU1F1 and PROP1 were studied in CPHD patients.

RESULTS

Of 102, 19.6% were familial cases. Height SDS, mean (SD) was - 5.14 (1.63). Peak GH, median (range) was 0.47 ng/ml (0-6.59), 72.5% patients had anterior pituitary hypoplasia (APH). Twenty mutations (novel: 11) were found in 43.1% patients (n = 44, IGHD-36, CPHD-8). GHRHR mutations (n = 32, p.Glu72* = 24) were more common than GH1 mutations (n = 4) in IGHD cohort. POU1F1 mutations (n = 6) were more common than PROP1 mutations (n = 2) in CPHD cohort. With few exceptions, this prevalence pattern is contrary to most studies in world-literature. No patients with peak GH > 4 ng/ml had mutations, signifying it as negative predictor. While many parameters were significant on univariate analysis, only positive family history and lower median peak GH levels were significant predictors of mutations on multivariate analysis in IGHD patients.

CONCLUSION

At variance with world literature, we found reverse predominance of GHRHR over GH1 mutations, POU1F1 over PROP1 mutations and predominance of GHRHR p.Glu72* mutations thus re-affirming the regional diversity in GHD genetics. We report positive and negative predictors of mutations in GHD.

Mutations Within the Transcription Factor PROP1 in a Cohort of Turkish Patients with Combined Pituitary Hormone Deficiency

OBJECTIVE

Mutations of the genes encoding transcription factors which play important roles in pituitary morphogenesis, differentiation and maturation may lead to combined pituitary hormone deficiency (CPHD). PROP1 gene mutations are reported as the most frequent genetic aetiology of CHPD. The aim of this study was to describe the phenotypes of Turkish CPHD patients and define the frequency of PROP1 mutations.

METHODS

Fifty-seven CPHD patients from 50 families were screened for PROP1 mutations. The patients were affected by growth hormone (GH) and additional anterior pituitary hormone deficiencies.

RESULTS

All patients had GH deficiency. In addition, 98.2% had central hypothyroidism, 45.6% had hypogonadotropic hypogonadism, 43.8% had adrenocorticotropic hormone deficiency and 7.1% had prolactin deficiency. Parental consanguinity rate was 50.9% and 14 cases were familial. Mean height standard deviation score (SDS) and weight SDS were -3.8±1.4 and -3.1±2.0, respectively. Of 53 patients with available pituitary imaging, 32 (60.4%) showed abnormalities. None had extra-pituitary abnormalities. Eight index patients had PROP1 gene mutations. Five sporadic patients were homozygous for c.301_302delAG (p.Leu102CysfsTer8) mutation, two siblings had exon 2 deletion, two siblings had complete gene deletion and two siblings were homozygous for the novel c.353A>G (p.Q118R) mutation. The frequency of the PROP1 mutations was 16% in our cohort. Mutation rate was significantly higher in familial cases compared to sporadic cases (42.8% vs 11.6%; p<0.01).

CONCLUSION

Phenotype of patients regarding hormonal deficiencies, pituitary morphology, presence of extra-pituitary findings, family history of CPHD and parental consanguinity are important for deciding which pituitary transcription factor deficiency should be investigated. PROP1 mutation frequencies vary in different populations and its prevalence is high in Turkish CPHD patients.

SEMA3A and IGSF10 Are Novel Contributors to Combined Pituitary Hormone Deficiency (CPHD)

Background: The mutation frequencies of pituitary transcription factors genes in patients with combined pituitary hormone deficiencies (CPHD) vary substantially between populations. However, apart from PROP1 the mutation rate of other genes is low and for almost half of the patients with CPHD the routine sequencing of known genes is unsuccessful in the identification of genetic causes. Methods: A cohort of 66 sporadic and nine familial CPHD cases (80 patients in total) were subjected to initial testing of the genes PROP1, POU1F1, LHX3, LHX4, and HESX1 using a targeted gene panel and MLPA. In patients who tested negative, a whole exome sequencing approach was employed. Results: In nine of the familial cases and 32 of the sporadic patients mutations in the PROP1 gene were found (the common pathogenic variants included c.301_302delAG and c.150delA). Mutations were also found in genes so far not related directly to CPHD. A unique homozygous and clinically relevant variant was identified in the SEMA3A gene, which may contribute to neural development and his phenotypic spectrum including short stature and isolated hypogonadotropic hypogonadism (IHH). Another pathogenic variant p.A1672T was found in the IGSF10 gene reported to be responsible for delayed puberty and neuronal migration during embryogenesis. Several suspected novel but predicted benign variants were also identified for the CHD7, WDR11 and FGF17 genes. Conclusion: Although PROP1 defects account for a majority of CPHD patients, identification of rare, less frequent variants constitutes a big challenge. Multiple genetic factors responsible for CPHD are still awaiting discovery and therefore the usage of efficient genomic tools (i.e., whole exome sequencing) will further broaden our knowledge regarding pituitary development and function.

A homozygous splice site ROBO1 mutation in a patient with a novel syndrome with combined pituitary hormone deficiency

The genetic causes of combined pituitary hormone deficiency remain elusive in most patients. Recently, incompletely penetrant heterozygous mutations in ROBO1 have been described in patients with pituitary stalk interruption syndrome. Herein, we identified a novel homozygous slice site mutation in ROBO1 (c.1342+1G>A) using a trio whole-exome sequencing strategy in a 5-year-old Japanese boy who had combined pituitary hormone deficiency, psychomotor developmental delay, severe intellectual disability, sensorineural hearing loss, strabismus, and characteristic facial features, including a broad forehead, micrognathia, and arched eyebrows. Magnetic resonance imaging delineated anterior pituitary hypoplasia, ectopic posterior pituitary, invisible pituitary stalk, thinning of the corpus callosum, and hypoplasia of the pons and midbrain. The phenotypically normal parents (first cousins) were heterozygous for the mutation. The results provide further evidence of ROBO1 being involved in the development of the pituitary gland. A recessive mutation of ROBO1 is a potential novel cause of a syndromic disorder associated with combined pituitary hormone deficiency.

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.

Necessity and Sufficiency of Ldb1 in the Generation, Differentiation and Maintenance of Non-photoreceptor Cell Types During Retinal Development

During mammalian retinal development, the multipotent progenitors differentiate into all classes of retinal cells under the delicate control of transcriptional factors. The deficiency of a transcription cofactor, the LIM-domain binding protein Ldb1, has been shown to cause proliferation and developmental defects in multiple tissues including cardiovascular, hematopoietic, and nervous systems; however, it remains unclear whether and how it regulates retinal development. By expression profiling, RNA in situ hybridization and immunostaining, here we show that Ldb1 is expressed in the progenitors during early retinal development, but later its expression gradually shifts to non-photoreceptor cell types including bipolar, amacrine, horizontal, ganglion, and Müller glial cells. Retina-specific ablation of Ldb1 in mice resulted in microphthalmia, optic nerve hypoplasia, retinal thinning and detachment, and profound vision impairment as determined by electroretinography. In the mutant retina, there was precocious differentiation of amacrine and horizontal cells, indicating a requirement of Ldb1 in maintaining the retinal progenitor pool. Additionally, all non-photoreceptor cell types were greatly reduced which appeared to be caused by a generation defect and/or retinal degeneration via excessive cell apoptosis. Furthermore, we showed that misexpressed Ldb1 was sufficient to promote the generation of bipolar, amacrine, horizontal, ganglion, and Müller glial cells at the expense of photoreceptors. Together, these results demonstrate that Ldb1 is not only necessary but also sufficient for the development and/or maintenance of non-photoreceptor cell types, and implicate that the pleiotropic functions of Ldb1 during retinal development are context-dependent and determined by its interaction with diverse LIM-HD (LIM-homeodomain) and LMO (LIM domain-only) binding protein partners.

Next generation sequencing panel based on single molecule molecular inversion probes for detecting genetic variants in children with hypopituitarism

BACKGROUND

Congenital Hypopituitarism is caused by genetic and environmental factors. Over 30 genes have been implicated in isolated and/or combined pituitary hormone deficiency. The etiology remains unknown for up to 80% of the patients, but most cases have been analyzed by limited candidate gene screening. Mutations in the PROP1 gene are the most common known cause, and the frequency of mutations in this gene varies greatly by ethnicity. We designed a custom array to assess the frequency of mutations in known hypopituitarism genes and new candidates, using single molecule molecular inversion probes sequencing (smMIPS).

METHODS

We used this panel for the first systematic screening for causes of hypopituitarism in children. Molecular inversion probes were designed to capture 693 coding exons of 30 known genes and 37 candidate genes. We captured genomic DNA from 51 pediatric patients with CPHD (n = 43) or isolated GH deficiency (IGHD) (n = 8) and their parents and conducted next generation sequencing.

RESULTS

We obtained deep coverage over targeted regions and demonstrated accurate variant detection by comparison to whole-genome sequencing in a control individual. We found a dominant mutation GH1, p.R209H, in a three-generation pedigree with IGHD.

CONCLUSIONS

smMIPS is an efficient and inexpensive method to detect mutations in patients with hypopituitarism, drastically limiting the need for screening individual genes by Sanger sequencing.

Genetic screening of regulatory regions of pituitary transcription factors in patients with idiopathic pituitary hormone deficiencies

PURPOSE

Mutation frequencies of PROP1, POU1F1 and HESX1 in patients with combined pituitary hormone deficiencies (CPHD) vary substantially between populations. They are low in sporadic CPHD patients in Western Europe. However, most clinicians still routinely send DNA of their CPHD patients for genetic screening of these pituitary transcription factors. Before we can recommend against screening of PROP1, POU1F1 and HESX1 as part of routine work-up for Western-European sporadic CPHD patients, it is crucial to rule out possible defects in regulatory regions of these genes, which could also disturb the complex process of pituitary organogenesis.

METHODS

The regulatory regions of PROP1, POU1F1 and HESX1 are not covered by Whole Exome Sequencing as they are largely located outside the coding regions. Therefore, we manually sequenced the regulatory regions, previously defined in the literature, of PROP1, POU1F1 and HESX1 among 88 Dutch patients with CPHD. We studied promoter SNPs in relation to phenotypic data.

RESULTS

We found six known SNPs in the PROP1 promoter. In the POU1F1 promoter, we found one new variant and two known SNPs. We did not find any variant in the HESX1 promoter.

CONCLUSION

Although the new POU1F1 variant might explain the phenotype of one patient, the general conclusion of this study is that variants in regulatory regions of PROP1, POU1F1 and HESX1 are rare in patients with sporadic CPHD in the Netherlands. We recommend that genetic screening of these pituitary transcription factors should no longer be part of routine work-up for Western-European, and especially Dutch, sporadic CPHD patients.

Contribution of LHX4 Mutations to Pituitary Deficits in a Cohort of 417 Unrelated Patients

CONTEXT

LHX4 encodes a LIM-homeodomain transcription factor that is implicated in early pituitary development. In humans, only 13 heterozygous LHX4 mutations have been associated with congenital hypopituitarism.

OBJECTIVE

The aims of this study were to evaluate the prevalence of LHX4 mutations in patients with hypopituitarism, to define the associated phenotypes, and to characterize the functional impact of the identified variants and the respective role of the 2 LIM domains of LHX4.

DESIGN AND PATIENTS

We screened 417 unrelated patients with isolated growth hormone deficiency or combined pituitary hormone deficiency associated with ectopic posterior pituitary and/or sella turcica anomalies for LHX4 mutations (Sanger sequencing). In vitro studies were performed to assess the functional consequences of the identified variants.

RESULTS

We identified 7 heterozygous variations, including p.(Tyr131*), p.(Arg48Thrfs*104), c.606+1G>T, p.Arg65Val, p.Thr163Pro, p.Arg221Gln, and p.Arg235Gln), that were associated with variable expressivity; 5 of the 7 were also associated with incomplete penetrance. The p.(Tyr131*), p.(Arg48Thrfs*104), p.Ala65Val, p.Thr163Pro, and p.Arg221Gln LHX4 variants are unable to transactivate the POU1F1 and GH promoters. As suggested by transactivation, subcellular localization, and protein-protein interaction studies, p.Arg235Gln is probably a rare polymorphism. Coimmunoprecipitation studies identified LHX3 as a potential protein partner of LHX4. As revealed by functional studies of LIM-defective recombinant LHX4 proteins, the LIM1 and LIM2 domains are not redundant.

CONCLUSION

This study, performed in the largest cohort of patients screened so far for LHX4 mutations, describes 6 disease-causing mutations that are responsible for congenital hypopituitarism. LHX4 mutations were found to be associated with variable expressivity, and most of them with incomplete penetrance; their contribution to pituitary deficits that are associated with an ectopic posterior pituitary and/or a sella turcica defect is ∼1.4% in the 417 probands tested.

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.

Interstitial duplication of chromosome region 1q25.1q25.3: report of a patient with mild cognitive deficits, tall stature and facial dysmorphisms

Isolated interstitial duplications of chromosome band 1q25 are apparently very rare; no patients with detailed molecular and clinical characterization of duplications restricted to this region have been published to date. We report on a 9-year-old girl with mild cognitive deficits, tall stature, macrocephaly and discrete dysmorphic features in whom a de novo interstitial 7.5 Mb duplication of 1q25.1q25.3 was detected by SNP array analysis (arr[hg19] 1q25.1q25.3(173,925,505-181,381,242)x3 dn). The duplicated region was inversely inserted into chromosome band 1q42.2: 46,XX,der(1)(pter→q42.2::q25.3→q25.1::q42.2→qter). Overexpression of one or several of the 87 genes in the duplicated interval was presumably the major causative factor for the clinical manifestations. Reports of additional patients with overlapping duplications will be needed to establish detailed karyotype-phenotype correlations and to gain a better understanding of the underlying pathomechanisms.

Frequency of genetic defects in combined pituitary hormone deficiency: a systematic review and analysis of a multicentre Italian cohort

OBJECTIVE

Combined pituitary hormonal deficiency (CPHD) can result from mutations within genes that encode transcription factors. This study evaluated the frequency of mutations in these genes in a cohort of 144 unrelated Italian patients with CPHD and estimated the overall prevalence of mutations across different populations using a systematic literature review.

MATERIAL AND METHODS

A multicentre study of adult and paediatric patients with CPHD was performed. The PROP1, POU1F1, HESX1, LHX3 and LHX4 genes were analysed for the presence of mutations using direct sequencing. We systematically searched PubMed with no date restrictions for studies that reported genetic screening of CPHD cohorts. We only considered genetic screenings with at least 10 individuals. Data extraction was conducted in accordance with the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

Global mutation frequency in Italian patients with CPHD was 2·9% (4/136) in sporadic cases and 12·5% (1/8) in familial cases. The worldwide mutation frequency for the five genes calculated from 21 studies was 12·4%, which ranged from 11·2% in sporadic to 63% in familial cases. PROP1 was the most frequently mutated gene in sporadic (6·7%) and familial cases (48·5%).

CONCLUSION

The frequency of defects in genes encoding pituitary transcription factors is quite low in Italian patients with CPHD and other western European countries, especially in sporadic patients. The decision of which genes should be tested and in which order should be guided by hormonal and imaging phenotype, the presence of extrapituitary abnormalities and the frequency of mutation for each gene in the patient-referring population.

ISL1 Is Necessary for Maximal Thyrotrope Response to Hypothyroidism

ISLET1 is a homeodomain transcription factor necessary for development of the pituitary, retina, motor neurons, heart, and pancreas. Isl1-deficient mice (Isl1(-/-)) die early during embryogenesis at embryonic day 10.5 due to heart defects, and at that time, they have an undersized pituitary primordium. ISL1 is expressed in differentiating pituitary cells in early embryogenesis. Here, we report the cell-specific expression of ISL1 and assessment of its role in gonadotropes and thyrotropes. Isl1 expression is elevated in pituitaries of Cga(-/-) mice, a model of hypothyroidism with thyrotrope hypertrophy and hyperplasia. Thyrotrope-specific disruption of Isl1 with Tshb-cre is permissive for normal serum TSH, but T4 levels are decreased, suggesting decreased thyrotrope function. Inducing hypothyroidism in normal mice causes a reduction in T4 levels and dramatically elevated TSH response, but mice with thyrotrope-specific disruption of Isl1 have a blunted TSH response. In contrast, deletion of Isl1 in gonadotropes with an Lhb-cre transgene has no obvious effect on gonadotrope function or fertility. These results show that ISL1 is necessary for maximal thyrotrope response to hypothyroidism, in addition to its role in development of Rathke's pouch.

Molecular screening of a large cohort of Moroccan patients with congenital hypopituitarism

BACKGROUND/OBJECTIVES

Congenital hypopituitarism is a rare disease which, for most patients, has no identified molecular cause. We aimed to document the molecular basis of growth retardation in a Moroccan cohort.

DESIGN/PATIENTS

80 index cases [54 with isolated growth hormone deficiency (IGHD), 26 with combined pituitary hormone deficiency (CPHD)] were screened for molecular defects in GH1 (including LCR-GH1), GHRHR, GHSR, GHRH, PROP1, POU1F1, HESX1, LHX3, LHX4 and SOX3.

RESULTS

Five different deleterious mutations were identified in 14 patients from eight families. In the IGHD group, three genes were found to be involved: GH1, GHRHR and GHSR. In the CPHD group, PROP1 was the only mutated gene. In addition, two heterozygous variations whose deleterious effect remains to be demonstrated were identified (in GH1 and LHX4), and two polymorphisms (missense variations) were detected (in LHX3 and in GHSR). The prevalence of mutations in this Moroccan GHD cohort was 10% (8/80), 11·1% (6/54) in the IGHD group and 7·7% (2/26) in the CPHD group.

CONCLUSION

This is the first molecular screening of congenital GHD in a Moroccan population and, like other studies, mutations were preferentially identified in familial cases (75%); mutations in genes such as POU1F1, HESX1, SOX3, LHX3 and LHX4 are extremely rare. The p.R73C PROP1 mutation was the most frequent mutation in CPHD; this should be the first one to screen in this population. Our results should contribute to a better diagnosis and management of this heterogeneous disease condition.

Novel Lethal Form of Congenital Hypopituitarism Associated With the First Recessive LHX4 Mutation

BACKGROUND

LHX4 encodes a member of the LIM-homeodomain family of transcription factors that is required for normal development of the pituitary gland. To date, only incompletely penetrant heterozygous mutations in LHX4 have been described in patients with variable combined pituitary hormone deficiencies.

OBJECTIVE/HYPOTHESIS

To report a unique family with a novel recessive variant in LHX4 associated with a lethal form of congenital hypopituitarism that was identified through screening a total of 97 patients.

METHOD

We screened 97 unrelated patients with combined pituitary hormone deficiency, including 65% with an ectopic posterior pituitary, for variants in the LHX4 gene using Sanger sequencing. Control databases (1000 Genomes, dbSNP, Exome Variant Server, ExAC Browser) were consulted upon identification of variants.

RESULTS

We identified the first novel homozygous missense variant (c.377C>T, p.T126M) in two deceased male patients of Pakistani origin with severe panhypopituitarism associated with anterior pituitary aplasia and posterior pituitary ectopia. Both were born small for gestational age with a small phallus, undescended testes, and mid-facial hypoplasia. The parents' first-born child was a female with mid-facial hypoplasia (DNA was unavailable). Despite rapid commencement of hydrocortisone and T4 in the brothers, all three children died within the first week of life. The LHX4(p.T126M) variant is located within the LIM2 domain, in a highly conserved location. The absence of homozygosity for the variant in over 65 000 controls suggests that it is likely to be responsible for the phenotype.

CONCLUSION

We report, for the first time to our knowledge, a novel homozygous mutation in LHX4 associated with a lethal phenotype, implying that recessive mutations in LHX4 may be incompatible with life.

Lhx4 deficiency: increased cyclin-dependent kinase inhibitor expression and pituitary hypoplasia

Defects in the Lhx4, Lhx3, and Pitx2 genes can cause combined pituitary hormone deficiency and pituitary hypoplasia in both humans and mice. Not much is known about the mechanism underlying hypoplasia in these mutants beyond generally increased cell death and poorly maintained proliferation. We identified both common and unique abnormalities in developmental regulation of key cell cycle regulator gene expression in each of these three mutants. All three mutants exhibit reduced expression of the proliferative marker Ki67 and the transitional marker p57. We discovered that expression of the cyclin-dependent kinase inhibitor 1a (Cdkn1a or p21) is expanded dorsally in the pituitary primordium of both Lhx3 and Lhx4 mutants. Uniquely, Lhx4 mutants exhibit reduced cyclin D1 expression and have auxiliary pouch-like structures. We show evidence for indirect and direct effects of LHX4 on p21 expression in αT3-1 pituitary cells. In summary, Lhx4 is necessary for efficient pituitary progenitor cell proliferation and restriction of p21 expression.

Sonic Hedgehog mutations are not a common cause of congenital hypopituitarism in the absence of complex midline cerebral defects

CONTEXT AND OBJECTIVE

Sonic Hedgehog (SHH) and GLI2, an obligatory mediator of SHH signal transduction, are holoprosencephaly (HPE)-associated genes essential in pituitary formation. GLI2 variants have been found in patients with congenital hypopituitarism without complex midline cerebral defects (MCD). However, data on the occurrence of SHH mutations in these patients are limited. We screened for SHH and GLI2 mutations or copy number variations (CNV) in patients with congenital hypopituitarism without MCD or with variable degrees of MCD.

PATIENTS AND METHODS

Detailed data on clinical, laboratory and neuroimaging findings of 115 patients presenting with congenital hypopituitarism without MCD, septo-optic dysplasia or HPE were analysed. The SHH and GLI2 genes were directly sequenced, and the presence of gene CNV was analysed by multiplex ligation-dependent probe amplification (MLPA).

RESULTS

Anterior pituitary deficiency was found in 74% and 53% of patients with SOD or HPE, respectively. Diabetes insipidus was common in patients with HPE (47%) but infrequent in patients with congenital hypopituitarism or SOD (7% and 8%, respectively). A single heterozygous nonsense SHH mutation (p.Tyr175Ter) was found in a patient presenting with hypopituitarism and alobar HPE. No other SHH mutations or CNV were found. Nine GLI2 variations (8 missense and 1 frameshift) including a homozygous and a compound heterozygous variation were found in patients with congenital hypopituitarism or SOD, but not in HPE patients. No GLI2 CNV were found.

CONCLUSION

SHH mutations or copy number variations are not a common cause of congenital hypopituitarism in patients without complex midline cerebral defects. GLI2 variants are found in some patients with congenital hypopituitarism without complex midline cerebral defects or septo-optic dysplasia. However, functional analyses of these variants are needed to strengthen genotype-phenotype relationship.

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.

Isolated central hypothyroidism in young siblings as a manifestation of PROP1 deficiency: clinical impact of whole exome sequencing

BACKGROUND/AIMS

Central hypothyroidism (CH) in children is rare and may be due to a variety of genetic defects. Most of these defects, but not all, are associated with additional pituitary hormone deficits. In a young child presenting with CH, it is important to determine whether additional pituitary hormone deficiencies are present, but this may be difficult to establish clinically.

METHODS

We describe the clinical characteristics of two young siblings, aged 6 months and 2 years, presenting with isolated CH. Whole exome sequencing was performed to determine the genetic basis of isolated CH.

RESULTS

A homozygous frameshift mutation of PROP1 (296delGA) was identified in both probands. Defects in PROP1 cause progressive deficiency of multiple pituitary hormones. Based on this genetic diagnosis, further clinical testing was performed that demonstrated growth hormone deficiency in one sibling.

CONCLUSIONS

PROP1 deficiency may present as isolated CH at a very young age. In disorders with multiple potential causative genes, whole exome sequencing may facilitate rapid genetic diagnosis and lead to important changes in clinical management.

Clinical utility of chromosomal microarray analysis

OBJECTIVE

To test the hypothesis that chromosomal microarray analysis frequently diagnoses conditions that require specific medical follow-up and that referring physicians respond appropriately to abnormal test results.

METHODS

A total of 46,298 postnatal patients were tested by chromosomal microarray analysis for a variety of indications, most commonly intellectual disability/developmental delay, congenital anomalies, dysmorphic features, and neurobehavioral problems. The frequency of detection of abnormalities associated with actionable clinical features was tallied, and the rate of physician response to a subset of abnormal tests results was monitored.

RESULTS

A total of 2088 diagnoses were made of more than 100 different disorders that have specific clinical features that warrant follow-up. The detection rate for these conditions using high-resolution whole-genome microarrays was 5.4%, which translates to 35% of all clinically significant abnormal test results identified in our laboratory. In a subset of cases monitored for physician response, appropriate clinical action was taken more than 90% of the time as a direct result of the microarray finding.

CONCLUSIONS

The disorders diagnosed by chromosomal microarray analysis frequently have clinical features that need medical attention, and physicians respond to the diagnoses with specific clinical actions, thus arguing that microarray testing provides clinical utility for a significant number of patients tested.

Gradual loss of ACTH due to a novel mutation in LHX4: comprehensive mutation screening in Japanese patients with congenital hypopituitarism

Mutations in transcription factors genes, which are well regulated spatially and temporally in the pituitary gland, result in congenital hypopituitarism (CH) in humans. The prevalence of CH attributable to transcription factor mutations appears to be rare and varies among populations.

This study aimed to define the prevalence of CH in terms of nine CH-associated genes among Japanese patients. We enrolled 91 Japanese CH patients for DNA sequencing of POU1F1, PROP1, HESX1, LHX3, LHX4, SOX2, SOX3, OTX2, and GLI2. Additionally, gene copy numbers for POU1F1, PROP1, HESX1, LHX3, and LHX4 were examined by multiplex ligation-dependent probe amplification. The gene regulatory properties of mutant LHX4 proteins were characterized in vitro. We identified two novel heterozygous LHX4 mutations, namely c.249-1G>A, p.V75I, and one common POU1F1 mutation, p.R271W. The patient harboring the c.249-1G>A mutation exhibited isolated growth hormone deficiency at diagnosis and a gradual loss of ACTH, whereas the patient with the p.V75I mutation exhibited multiple pituitary hormone deficiency. In vitro experiments showed that both LHX4 mutations were associated with an impairment of the transactivation capacities of POU1F1 andαGSU, without any dominant-negative effects. The total mutation prevalence in Japanese CH patients was 3.3%. This study is the first to describe, a gradual loss of ACTH in a patient carrying an LHX4 mutation. Careful monitoring of hypothalamic–pituitary -adrenal function is recommended for CH patients with LHX4 mutations.

Functional SNPs within the intron 1 of the PROP1 gene contribute to combined growth hormone deficiency (CPHD)

CONTEXT

Mutations within the PROP1 gene represent one of the main causes of familial combined pituitary hormone deficiency (CPHD). However, most of the cases are sporadic with an unknown genetic cause.

OBJECTIVE

The aim of this study was the search for low penetrance variations within and around a conserved regulatory element in the intron 1 of PROP1, contributing to a multifactorial form of the disease in sporadic patients.

METHODS AND PATIENTS

A fragment of 570 bp encompassing the conserved region was sequenced in 107 CPHD patients and 294 controls, and an association study was performed with the four identified variants, namely c.109+435G>A (rs73346254), c.109+463C>T (rs4498267), c.109+768C>G (rs4431364), and c.109+915_917ins/delTAG (rs148607624). The functional role of the associated polymorphisms was evaluated by luciferase reporter gene expression analyses and EMSA.

RESULTS

A statistically significant increased frequency was observed in the patients for rs73346254A (P = 5 × 10(-4)) and rs148607624delTAG (P = 0.01) alleles. Among all the possible allele combinations, only the haplotype bearing both risk alleles showed a significantly higher frequency in the patients vs. controls (P = 4.7 × 10(-4)) and conferred a carrier risk of 4.19 (P = 1.2 × 10(-4)). This haplotype determined a significant decrease of the luciferase activity in comparison with a basal promoter and the other allelic combinations in GH4C and MCF7 cells (P = 4.6 × 10(-6); P = 5.5 × 10(-4), respectively). The EMSA showed a differential affinity for nuclear proteins for the alternative alleles of the two associated variations.

CONCLUSIONS

Variations with a functional significance conferring susceptibility to CPHD have been identified in the PROP1 gene, indicating a multifactorial origin of this disorder in sporadic cases.

High resolution array in the clinical approach to chromosomal phenotypes

Array genomic hybridization (AGH) has recently been implemented as a diagnostic tool for the detection of submicroscopic copy number variants (CNVs) in patients with developmental disorders. However, there is no consensus regarding the choice of the platform, the minimal resolution needed and systematic interpretation of CNVs. We report our experience in the clinical diagnostic use of high resolution AGH up to 100 kb on 131 patients with chromosomal phenotypes but previously normal karyotype. We evaluated the usefulness in our clinics and laboratories by the detection rate of causal CNVs and CNVs of unknown clinical significance and to what extent their interpretation would challenge the systematic use of high-resolution arrays in clinical application. Prioritizing phenotype-genotype correlation in our interpretation strategy to criteria previously described, we identified 33 (25.2%) potentially pathogenic aberrations. 16 aberrations were confirmed pathogenic (16.4% syndromic, 8.5% non-syndromic patients); 9 were new and individual aberrations, 3 of them were pathogenic although inherited and one is as small as approx 200 kb. 13 of 16 further CNVs of unknown significance were classified likely benign, for 3 the significance remained unclear. High resolution array allows the detection of up to 12.2% of pathogenic aberrations in a diagnostic clinical setting. Although the majority of aberrations are larger, the detection of small causal aberrations may be relevant for family counseling. The number of remaining unclear CNVs is limited. Careful phenotype-genotype correlations of the individual CNVs and clinical features are challenging but remain a hallmark for CNV interpretation.

The use of neuroimaging for assessing disorders of pituitary development

Magnetic resonance imaging (MRI) is the radiological examination method of choice for evaluating hypothalamo-pituitary-related endocrine disease and is considered essential in the assessment of patients with suspected hypothalamo-pituitary pathology. Physicians involved in the care of such patients have, in MRI, a valuable tool that can aid them in determining the pathogenesis of their patients' underlying pituitary conditions. Indeed, the use of MRI has led to an enormous increase in our knowledge of pituitary morphology, improving, in particular, the differential diagnosis of hypopituitarism. Specifically, MRI allows detailed and precise anatomical study of the pituitary gland by differentiating between the anterior and posterior pituitary lobes. MRI recognition of pituitary hyperintensity in the posterior part of the sella, now considered a marker of neurohypophyseal functional integrity, has been the most striking finding in the diagnosis and understanding of certain forms of 'idiopathic' and permanent growth hormone deficiency (GHD). Published data show a number of correlations between pituitary abnormalities as observed on MRI and a patient's endocrine profile. Indeed, several trends have emerged and have been confirmed: (i) a normal MRI or anterior pituitary hypoplasia generally indicates isolated growth hormone deficiency that is mostly transient and resolves upon adult height achievement; (ii) patients with multiple pituitary hormone deficiencies (MPHD) seldom show a normal pituitary gland; and (iii) the classic triad of ectopic posterior pituitary, pituitary stalk hypoplasia/agenesis and anterior pituitary hypoplasia is more frequently reported in MPHD patients and is generally associated with permanent GHD. Pituitary abnormalities have also been reported in patients with hypopituitarism carrying mutations in several genes encoding transcription factors. Establishing endocrine and MRI phenotypes is extremely useful for the selection and management of patients with hypopituitarism, both in terms of possible genetic counselling and in the early diagnosis of evolving anterior pituitary hormone deficiencies. Going forward, neuroimaging techniques are expected to progressively expand and improve our knowledge and understanding of pituitary diseases.

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.

Panhypopituitarism presenting as life-threatening heart failure caused by an inherited microdeletion in 1q25 including LHX4

Clinical presentation of hypopituitarism in the neonate may be variable, ranging from absent to severe nonspecific symptoms and may be life-threatening in patients with adrenocorticotropic hormone deficiency. The LIM homeobox gene 4 (LHX4) transcription factor regulates early embryonic development of the anterior pituitary gland. Autosomal dominant mutations in LHX4 cause congenital hypopituitarism with variable combined pituitary hormone deficiency (CPHD). We report on a neonate with unexplained heart failure and minor physical anomalies, suggesting a midline defect. She was diagnosed with complete CPHD. Cardiac function was rescued by replacement with hydrocortisone and thyroxine; hypoglycaemia stopped under growth hormone therapy. Magnetic resonance imaging revealed a dysgenetic pituitary gland suggesting an early developmental defect. Array comparative genomic hybridization showed a maternally inherited 1.5-megabase microdeletion in 1q25.2q25.3, including the LHX4 gene. Haploinsufficiency of LHX4 likely explains the predominant pituitary phenotype in the proposita and we suggest variable intrafamilial penetrance of the inherited microdeletion. To the best of our knowledge, we are the first to report on heart failure as a rare nonspecific symptom of treatable CPHD in the newborn. Variably penetrant pituitary insufficiency, including this severe and atypical presentation, can be correlated with LHX4 insufficiency and highlights the role of LHX4 for pituitary development.

X-linked recessive combined pituitary hormone deficiency is mapped to Xp22.3-Xp11 in a Chinese family

Genetic mutations have been identified in a modest proportion of patients with combined pituitary hormone deficiency (CPHD). We reported a 3-generation family consisting of 18 members, including 5 affected males (the proband, his 2 brothers, his cousin, and his maternal uncle; III1-III4, II8) suffered with CPHD. MRI of the pituitary gland showed hypoplasia of the pituitary gland in affected members. By 19 STR markers and linkage analysis, we found that the disease gene localized between the DXS987 and DXS1226 markers (LOD score=2.408, θ=0). All affected male patients inherited the same haplotype from the female carrier (I4). The proband's mother (II4) and her sister (II3, II6) were obligate female carriers. However, the unaffected males (II(7), II(9)) in the family did not have this haplotype. These observations confirm a new X-linked recessive inherited disease in a Chinese family with CPHD and the pathogenic gene is mapped to Xp22.1-Xp11.

Isolated GH deficiency: mutation screening and copy number analysis of HMGA2 and CDK6 genes

OBJECTIVE

In most patients, the genetic cause of isolated GH deficiency (IGHD) is unknown. By identifying several genes associated with height variability within the normal population, three separate genome-wide association studies provided new candidate genes for human growth disorders. We selected two of them for genetic screening of our IGHD population.

AIM

We aimed to determine whether high-mobility group A2 (HMGA2) and cyclin-dependent protein kinase 6 (CDK6) are involved in the pathogenicity of IGHD.

METHODS

We directly sequenced coding regions and exon-intron boundaries of the genes HMGA2 and CDK6 in 105 Caucasian IGHD patients from the Dutch HYPOPIT study. In addition, we developed a new probe set of multiplex ligation-dependent probe amplification for both genes in order to detect copy number variations.

RESULTS

In one patient with classical IGHD phenotype, we identified a new heterozygous 20 bp deletion in the intronic region of HMGA2 (c.250-29_-9del), which was absent in the databases and healthy controls. Together, with recently published data concerning the 12q14 microdeletion syndrome, where patients with an HMGA2 haploinsufficiency had proportionate short stature, this study provides further support of the important role for HMGA2 in growth. In CDK6, we found only known polymorphisms.

CONCLUSIONS

This study provides the first report of a deletion in the HMGA2 gene that might be related to IGHD. We suggest that this gene is investigated as a second screening in patients with a classical IGHD phenotype in which mutations in classical candidate genes have been excluded.

The role of homeodomain transcription factors in heritable pituitary disease

The anterior pituitary gland secretes hormones that regulate developmental and physiological processes, including growth, the stress response, metabolic status, reproduction and lactation. During embryogenesis, cellular determination and differentiation events establish specialized hormone-secreting cell types within the anterior pituitary gland. These developmental decisions are mediated in part by the actions of a cascade of transcription factors, many of which belong to the homeodomain class of DNA-binding proteins. The discovery of some of these regulatory proteins has facilitated genetic analyses of patients with hormone deficiencies. The findings of these studies reveal that congenital defects-ranging from isolated hormone deficiencies to combined pituitary hormone deficiency syndromes-are sometimes associated with mutations in the genes encoding pituitary-acting developmental transcription factors. The phenotypes of affected individuals and animal models have together provided useful insights into the biology of these transcription factors and have suggested new hypotheses for testing in the basic science laboratory. Here, we summarize the gene regulatory pathways that control anterior pituitary development, with emphasis on the role of the homeodomain transcription factors in normal pituitary organogenesis and heritable pituitary disease.

Pituitary transcription factors in the aetiology of combined pituitary hormone deficiency

The somatotropic axis is the central postnatal regulator of longitudinal growth. One of its major components--growth hormone--is produced by the anterior lobe of the pituitary, which also expresses and secretes five additional hormones (prolactin, thyroid stimulating hormone, follicle stimulating hormone, luteinizing hormone, adrenocorticotropic hormone). Proper development of the pituitary assures the regulation of critical processes such as metabolic control, puberty and reproduction, stress response and lactation. Ontogeny of the adenohypophysis is orchestrated by inputs from neighbouring tissues, cellular signalling molecules and transcription factors. Perturbation of expression or function of these factors has been implicated in the aetiology of combined pituitary hormone deficiency (CPHD). Mutations within the genes encoding for the transcription factors LHX3, LHX4, PROP1, and POU1F1 (PIT1) that act at different stages of pituitary development result in unique patterns of hormonal deficiencies reflecting their differential expression during organogenesis. In the case of LHX3 and LHX4 the phenotype may include extra-pituitary manifestations due to the function of these genes/proteins outside the pituitary gland. The remarkable variability in the clinical presentation of affected patients indicates the influence of the genetic background, environmental factors and possibly stochastic events. However, in the majority of CPHD cases the aetiology of this heterogeneous disease remains unexplained, which further suggests the involvement of additional genes. Identification of these factors might also help to close the gaps in our understanding of pituitary development, maintenance and function.