Mutations in hepatocyte nuclear factor-1beta and their related phenotypes

A genetic link between type 2 diabetes and prostate cancer

Epidemiological studies suggest that men with type 2 diabetes are less likely than non-diabetic men to develop prostate cancer. The cause of this association is not known. Recent genetic studies have highlighted a potential genetic link between the two diseases. Two studies have identified a version (allele) of a variant in the HNF1B (also known as TCF2) gene that predisposes to type 2 diabetes, and one of them showed that the same allele protects men from prostate cancer. Other, separate, studies have identified different variants in the JAZF1 gene, one associated with type 2 diabetes, another associated with prostate cancer. These findings are unlikely to completely explain the epidemiological association between the two diseases but they provide new insight into a possible direct causal link, rather than one that is confounded or biased in some way.

Reduced pancreatic volume in hepatocyte nuclear factor 1A-maturity-onset diabetes of the young

CONTEXT

There are interplays between the endocrine and exocrine pancreas. We recently reported an increased frequency of exocrine dysfunction in HNF1A-maturity-onset diabetes of the young (MODY3) patients, compared with controls. Reduced pancreatic volume is seen in HNF1B-MODY (MODY5) and diabetes types 1 and 2.

OBJECTIVE

The aim of this study was to investigate whether HNF1A mutation carriers have reduced pancreatic volume or abnormal pancreatic structure and whether any changes are associated with exocrine dysfunction.

METHODS

Fifteen HNF1A mutation carriers recruited from the Norwegian MODY Registry, 31 subjects with type 1 diabetes, 10 subjects with type 2 diabetes, and 11 controls underwent computed tomography of the pancreas. We measured pancreatic volume and X-ray attenuation. Pancreatic volume index was defined as pancreatic volume divided by body surface area.

RESULTS

Pancreatic volume index was reduced in subjects with HNF1A-MODY (34.5 ml/m2; P < 0.02) and type 1 diabetes (21.4 ml/m2; P < 0.001) as compared with nondiabetic controls (45.7 ml/m2), and was reduced in subjects with diabetes in combination with fecal elastase deficiency (P = 0.03). Subjects with type 1 diabetes had smaller pancreatic volume index, compared with HNF1A mutation carriers (P < 0.001). Reduced pancreatic volume index was associated with increasing duration of diabetes. Pancreatic X-ray attenuation in HNF1A mutation carriers was not significantly different from that of nondiabetic controls.

CONCLUSIONS

HNF1A mutation carriers have reduced pancreatic volume but less reduced than in patients with type 1 diabetes. Insulinopenia could explain both the pancreatic volume reduction and the associated pancreatic dysfunction.

Monogenic β-cell dysfunction in children: clinical phenotypes, genetic etiology and mutational pathways

Monogenic diabetes accounts for 1–2% of all cases of diabetes mellitus and presentation is often in childhood. Recognizing the clinical features of monogenic β-cell dysfunction prevents misdiagnosis and allows for more effective management and genetic counseling. Monogenic β-cell dysfunction is a diverse collection of clinical phenotypes underpinned by common mutational pathways. Mutations affecting the glycolytic glucokinase enzyme, the mitochondria, the KATP channels and transcription factors have been known for some time. Until recently, the role of endoplasmic reticulum stress was underestimated in the pathogenesis of diabetes. It is becoming increasingly clear that endoplasmic reticulum stress is an important etiological factor in the development of monogenic and polygenic diabetes. In this article, we aim to define the etiology of pediatric monogenic β-cell dysfunction and provide guidance on the investigation and management of children presenting with monogenic β-cell dysfunction.

Glomerulocystic kidney disease in hypomelanosis of Ito

Hypomelanosis of Ito (incontinentia pigmenti type I) was first described as a disorder characterized by unusual unilateral or bilateral cutaneous macular hypopigmented whorls, streaks and patches. Subsequently, neurologic, skeletal and ocular involvement were described. Kidney involvement has been reported only exceptionally. Here, we describe the case of a male infant with hypomelanosis of Ito with a prenatal diagnosis of bilateral enlargement of the kidneys, decreased corticomedullary differentiation and cysts located in the cortical and subcapsular regions. These findings were confirmed postnatally. The skin examination showed hypopigmented linear and round diffuse lesions located on the right leg and the arms. Ophthalmological examination showed anterior capsular and posterior subcapsular cataract of the left eye. Renal biopsy was characteristic of glomerulocystic kidney disease, whereas the skin biopsy confirmed the clinical diagnosis of hypomelanosis of Ito. Four other cases of kidney disease in hypomelanosis of Ito have been reported, including two cases characterized by cystic renal changes, indicating that gene abnormalities that cause hypomelanosis of Ito may also impair normal renal development, causing renal cystic changes.

Role of HNF-1α and HNF-1β on insulin, IGF-1 and other potential target genes

Hepatocyte nuclear factor (HNF)-1α and HNF-1β are transcription factors that regulate many target genes in various tissues including liver, pancreas and kidney. Heterozygous mutations in the HNF-1α and HNF-1β genes result in maturity-onset diabetes of the young (MODY)3 and MODY5, respectively. The discovery of these 'hepatocyte nuclear factors' as MODY-responsible genes provided a breakthrough in the field of diabetes. Patients with HNF-1α and HNF-1β mutations, as well as their model mice, show impaired pancreatic β-cell function. The mechanism of impaired β-cell function and the target genes has been intensively investigated by considerable in vitro and in vivo studies. The insulin gene is one of the target genes of HNF-1α and HNF-1β in the β-cells, and may contribute to the diabetes. The IGF-1 gene is also regulated by HNF-1α and HNF-1β, and its decreased expression may contribute to growth failure and impaired β-cell proliferation. Mutations in HNF-1β result in symptoms in multiple organs, including kidney and liver, and several target genes have been reported to be involved in the pathogenesis. HNF-1α and HNF-1β may be one of the master regulators of hepatocyte and islet transcription, and further investigations by microarray and genome-scale analyses are providing information for the better understanding of the complex transcriptional network involving HNF-1α and -1β.

Pelvic endometriosis is rarely associated with ovarian borderline tumours, cytologic and architectural atypia: a clinicopathologic study

Endometriotic foci, especially ovarian ones, with epithelial cytologic atypia may be precursors of cancer. This study presents an overview of the atypical cytological and histopathological findings associated with endometriosis. Six cases of endometriosis, with atypical histological and cytological changes, were obtained from the archives of the Department of Pathology at Cleveland Clinic Foundation between year 2000 and 2003. The size of the base from which these cases were drawn was 2000 cases of endometriosis. The age range of the patients was from 29 to 52 years. The clinical presentations included infertility (three cases), pelvic pain (three cases), adenexal and pelvic masses (four cases). Stage IV endometriosis with extensive pelvic involvement was found in two patients. Intraoperatively, the endometriotic lesions involved the ovaries (all cases); Cul de sac (four cases); urinary bladder (two cases); sigmoid colon, hemidiaphragms, and uterine vessels (one case each). The endometriotic lesions were associated with uterine leiomyomas (two patients) and adenocarcinoma of the vagina (one patient). Histologically, in addition to endometrial type glands and stroma, usually found in endometriosis, we observed both cytologic and pattern atypism involving the epithelium in all cases. The features of cytologic atypia included nuclear stratification, hyperchromatism, and pleomorphism. The features of pattern atypia were complex glandular pattern, papillary formations and psammoma bodies. In two cases, these features were sufficient for diagnosis of borderline Mullerian seromucinous tumours. One patient had recurred with metastatic adenocarcinoma of the vault. She died later from disseminated metastatic disease. There is a rare association between pelvic endometriosis and borderline ovarian tumours (three cases), cytologic and pattern atypia (two cases); mesothelial hyperplasia, endosalpingiosis (two cases), and metastasis (one case). Cytologic and pattern atypia can develop in the endometriotic foci and therefore, these lesions should be thoroughly scrutinized for presence of these changes. Our findings recommend surgical excision of these foci rather than their simple cauterization.

Dysplastic kidneys

Dysplastic kidneys are common malformations affecting up to 1 in 1000 of the general population. They are part of the spectrum of Congenital Abnormalities of the Kidney and Urinary Tract (CAKUT) and an increasing number of children are being diagnosed on antenatal ultrasound. In the past, these patients may not have been detected until adulthood following investigation for other illness, or even as incidental findings at post mortem, unless there was severe bilateral dysplasia leading to Potter's sequence or renal failure in childhood. Excluding syndromic cases with defects in other organ systems, features linked to worse prognosis at presentation are: (1) bilateral disease; (2) decreased functional renal mass (which encompasses not just small kidneys but also large ones where cysts replace normal architecture); (3) lower urinary tract obstruction; and (4) anhydramnios or severe oligohydramnios. Dysplasia and renal function are dynamic and can evolve during pregnancy, so repeated assessment is necessary when pathology is expected. Worsening dimensions or decreasing amniotic fluid levels imply poorer prognosis, but there are no proven therapies during pregnancy, though vesicoamniotic shunting may be indicated with obstruction. Postnatal investigations aim to define the anatomy, which helps to estimate risks of infection and kidney function. Management might then involve observation, prophylactic antibiotics, surgery and/or renal support. Risks of renal malignancy and hypertension are low during childhood, but longer-term follow-up is needed, particularly to determine blood pressure and renal function in adulthood and pregnancy. Around 10% of cases have a family history of significant renal/urinary tract malformation. Monogenic causes include mutations in individual genes, such as TCF2/hepatocyte nuclear factor 1ss (HNF1beta), PAX2 and uroplakins, but there are also recent reports of children with compound heterozygote mutations in several renal/urinary tract developmental genes. Effective genetic screening in future may require gene chip or other techniques to assess multiple genes concurrently, but this should not replace a multidisciplinary approach to these often difficult cases.

Genetic syndromes and prenatally detected renal anomalies

Renal anomalies are frequently detected on the routine second trimester scan offered to all pregnant women in the UK. These anomalies may be isolated but can also be associated with other congenital anomalies. Many combinations of ultrasound scan findings constitute recognised genetic entities. Knowledge of these conditions is essential for adequate management of the pregnancy and subsequent balanced parental counselling. This short review discusses the common genetic syndromes associated with the renal abnormalities identified on the antenatal ultrasound scan, and also provides an overview of renal symptoms in chromosome imbalances and after teratogenic influences.

Function of HNF1 in the pathogenesis of diabetes

The importance of hepatocyte nuclear factors (HNFs), as well as other transcription factors in β-cell development and function, was underlined by the characterization of human mutations causing maturity-onset diabetes of the young (MODY). HNF1A and HNF1B mutations lead to MODY forms 3 and 5, respectively. Thus, transcriptional control is an essential mechanism underlying the precise metabolic control exerted by β-cells in regulating insulin release. The diabetes phenotype of MODY3 (HNF1α) and the phenotypes of MODY5 (HNF1β), which can also include renal disease and genitourinary malformations, as well as neonatal diabetes and pancreatic agenesis, have now been described. However, detailed molecular pathology remains elusive. The large array of dominant-negative and deletion mutations, and the lack of structure-phenotype relationships for most mutations, have not helped us to formulate a mechanistic understanding. Further molecular studies of HNF1 actions and gene regulation are anticipated to provide useful insights into β-cell biology and potential therapeutic tools.

Transcription factor HNF1beta and novel partners affect nephrogenesis

Heterozygous mutations of the tissue-specific transcription factor hepatocyte nuclear factor (HNF)1beta, cause maturity onset diabetes of the young (MODY5) and kidney anomalies including agenesis, hypoplasia, dysplasia and cysts. Because of these renal anomalies, HNF1beta is classified as a CAKUT (congenital anomalies of the kidney and urinary tract) gene. We searched for human fetal kidney proteins interacting with the N-terminal region of HNF1beta using a bacterial two-hybrid system and identified five novel proteins along with the known partner DCoH. The interactions were confirmed for four of these proteins by GST pull-down assays. Overexpression of two proteins, E4F1 and ZFP36L1, in Xenopus embryos interfered with pronephros formation. Further, in situ hybridization showed overlapping expression of HNF1beta, E4F1 and ZFP36L1 in the developing pronephros. HNF1beta is present largely in the nucleus where it colocalized with E4F1. However, ZFP36L1 was located predominantly in the cytoplasm. A nuclear function for ZFP36L1 was shown as it was able to reduce HNF1beta transactivation in a luciferase reporter system. Our studies show novel proteins may cooperate with HNF1beta in human metanephric development and propose that E4F1 and ZFP36L1 are CAKUT genes. We searched for mutations in the open reading frame of the ZFP36L1 gene in 58 patients with renal anomalies but found none.

Best practice guidelines for the molecular genetic diagnosis of maturity-onset diabetes of the young

AIMS/HYPOTHESIS

Mutations in the GCK and HNF1A genes are the most common cause of the monogenic forms of diabetes known as 'maturity-onset diabetes of the young'. GCK encodes the glucokinase enzyme, which acts as the pancreatic glucose sensor, and mutations result in stable, mild fasting hyperglycaemia. A progressive insulin secretory defect is seen in patients with mutations in the HNF1A and HNF4A genes encoding the transcription factors hepatocyte nuclear factor-1 alpha and -4 alpha. A molecular genetic diagnosis often changes management, since patients with GCK mutations rarely require pharmacological treatment and HNF1A/4A mutation carriers are sensitive to sulfonylureas. These monogenic forms of diabetes are often misdiagnosed as type 1 or 2 diabetes. Best practice guidelines for genetic testing were developed to guide testing and reporting of results.

METHODS

A workshop was held to discuss clinical criteria for testing and the interpretation of molecular genetic test results. The participants included 22 clinicians and scientists from 13 countries. Draft best practice guidelines were formulated and edited using an online tool (http://www.coventi.com).

RESULTS

An agreed set of clinical criteria were defined for the testing of babies, children and adults for GCK, HNF1A and HNF4A mutations. Reporting scenarios were discussed and consensus statements produced.

CONCLUSIONS/INTERPRETATION

Best practice guidelines have been established for monogenic forms of diabetes caused by mutations in the GCK, HNF1A and HNF4A genes. The guidelines include both diagnostic and predictive genetic tests and interpretation of the results.

Phenotype of a patient with a de novo mutation in the hepatocyte nuclear factor 1beta/maturity-onset diabetes of the young type 5 gene

Mutations in the gene encoding the transcription factor hepatocyte nuclear factor (HNF) 1beta cause various phenotypes including maturity-onset diabetes of the young type 5 (MODY5) and kidney disease. We provide molecular and pathophysiologic characterization of a 23-year-old male patient with clinical presentation typical for MODY5 with renal involvement. Clinical studies (including intravenous glucose tolerance test and magnetic resonance imaging) of the patient and 5 family members in comparison with unrelated control subjects and molecular analysis of the HNF-1beta gene (direct sequencing, paternity testing, and restriction fragment length polymorphism analysis for parental mosaicism) were performed. The patient was born with low birth weight (2250 g), whereas his dizygotic twin sister was of normal weight (3500 g) and healthy. He had cystic renal dysplasia with progressive renal failure and pancreas atrophy with beta-cell dysfunction and early-onset diabetes mellitus but no family history of diabetes. Intravenous glucose tolerance test showed a markedly reduced but not absent acute insulin response compared with controls (n = 6). A mutation in the HNF-1beta gene S148L (C443T) in exon 2 within the pseudo-POU domain was identified. All other family members and the control group (n = 255) did not have the mutation, suggesting that we described a de novo mutation in HNF-1beta. Paternity was confirmed, and no signs of mosaicism in DNA analysis of both parents could be detected. Of note, the low birth weight of the patient in contrast to his healthy twin sister provides interesting support for the fetal insulin hypothesis for reduced birth weight.

Clinical implications of a molecular genetic classification of monogenic beta-cell diabetes

Monogenic diabetes resulting from mutations that primarily reduce beta-cell function accounts for 1-2% of diabetes cases, although it is often misdiagnosed as either type 1 or type 2 diabetes. Knowledge of the genetic etiology of diabetes enables more-appropriate treatment, better prediction of disease progression, screening of family members and genetic counseling. We propose that the old clinical classifications of maturity-onset diabetes of the young and neonatal diabetes are obsolete and that specific genetic etiologies should be sought in four broad clinical situations because of their specific treatment implications. Firstly, diabetes diagnosed before 6 months of age frequently results from mutation of genes that encode Kir6.2 (ATP-sensitive inward rectifier potassium channel) or sulfonylurea receptor 1 subunits of an ATP-sensitive potassium channel, and improved glycemic control can be achieved by treatment with high-dose sulfonylureas rather than insulin. Secondly, patients with stable, mild fasting hyperglycemia detected particularly when they are young could have a glucokinase mutation and might not require specific treatment. Thirdly, individuals with familial, young-onset diabetes that does not fit with either type 1 or type 2 diabetes might have mutations in the transcription factors HNF-1alpha (hepatocyte nuclear factor 1-alpha) or HNF-4alpha, and can be treated with low-dose sulfonylureas. Finally, extrapancreatic features, such as renal disease (caused by mutations in HNF-1beta) or deafness (caused by a mitochondrial m.3243A>G mutation), usually require early treatment with insulin.

Mutations of HNF-1beta inhibit epithelial morphogenesis through dysregulation of SOCS-3

Hepatocyte nuclear factor-1beta (HNF-1beta) is a Pit-1, Oct-1/2, Unc-86 (POU) homeodomain-containing transcription factor expressed in the kidney, liver, pancreas, and other epithelial organs. Mutations of HNF-1beta cause maturity-onset diabetes of the young, type 5 (MODY5), which is characterized by early-onset diabetes mellitus and congenital malformations of the kidney, pancreas, and genital tract. Knockout of HNF-1beta in the mouse kidney results in cyst formation. However, the signaling pathways and transcriptional programs controlled by HNF-1beta are poorly understood. Using genome-wide chromatin immunoprecipitation and DNA microarray (ChIP-chip) and microarray analysis of mRNA expression, we identified SOCS3 (suppressor of cytokine signaling-3) as a previously unrecognized target gene of HNF-1beta in the kidney. HNF-1beta binds to the SOCS3 promoter and represses SOCS3 transcription. The expression of SOCS3 is increased in HNF-1beta knockout mice and in renal epithelial cells expressing dominant-negative mutant HNF-1beta. Increased levels of SOCS-3 inhibit HGF-induced tubulogenesis by decreasing phosphorylation of Erk and STAT-3. Conversely, knockdown of SOCS-3 in renal epithelial cells expressing dominant-negative mutant HNF-1beta rescues the defect in HGF-induced tubulogenesis by restoring phosphorylation of Erk and STAT-3. Thus, HNF-1beta regulates tubulogenesis by controlling the levels of SOCS-3 expression. Manipulating the levels of SOCS-3 may be a useful therapeutic approach for human diseases induced by HNF-1beta mutations.

Structural basis of disease-causing mutations in hepatocyte nuclear factor 1beta

HNF1beta is an atypical POU transcription factor that participates in a hierarchical network of transcription factors controlling the development and proper function of vital organs such as liver, pancreas, and kidney. Many inheritable mutations on HNF1beta are the monogenic causes of diabetes and several kidney diseases. To elucidate the molecular mechanism of its function and the structural basis of mutations, we have determined the crystal structure of human HNF1beta DNA binding domain in complex with a high-affinity promoter. Disease-causing mutations have been mapped to our structure, and their predicted effects have been tested by a set of biochemical/ functional studies. These findings together with earlier findings with a homologous protein HNF1alpha, help us to understand the structural basis of promoter recognition by these atypical POU transcription factors and the site-specific functional disruption by disease-causing mutations.

Mutations in GCK and HNF-1alpha explain the majority of cases with clinical diagnosis of MODY in Spain

OBJECTIVE

The aim of this study was to group patients with MODY (maturity-onset diabetes of the young) according to the genetic alterations underlying the disease and to investigate their clinical characteristics.

PATIENTS AND METHODS

Molecular analysis of GCK (MODY2), HNF-1alpha (MODY3), HNF-4alpha (MODY1) and HNF-1beta (MODY5) genes was performed by DNA sequencing in 95 unrelated index probands (47M/48F; mean age 9.9 +/- 5.2 years) with clinical diagnosis of MODY. After classification into MODY subtypes according to the genetic alterations, clinical characteristics were compared between the groups.

RESULTS

Seventy-six families were shown to carry mutations in GCK (34 of them previously unreported), eight families presented HNF-1alpha mutations, and a large genomic rearrangement in HNF-1beta was found in a family. No alteration was found in HNF-4alpha. Thus, relative frequencies in the group studied were 80% MODY2, 8.5% MODY3 and 1% MODY5. Comparison of clinical parameters according to genetic status showed significant differences between MODY2 and MODY3 patients in age at diagnosis (9.4 +/- 5.4 years vs. 12.7 +/- 4.6 years), diagnosis (impaired glucose tolerance vs. diabetes), diagnostic test used (OGTT vs. fasting glucose), treatment (diet and exercise vs. insulin/oral antidiabetic agents) and birth weight (2.96 +/- 0.44 kg vs. 3.40 +/- 0.67 kg).

CONCLUSION

Almost 90% of the MODY cases in the group studied are explained by mutations in the major genes GCK (MODY2) and HNF-1alpha(MODY3), although differences in the relative prevalence of each form could be partly due to patient referral bias (paediatric vs. adult). In general, patients with MODY2 were diagnosed at an earlier age in life than MODY3 patients and had a milder form of diabetes. Moreover, the majority of patients with MODY2 mutations were treated with diet whereas half of MODY3 patients received pharmacological treatment.

Monogenic disorders of the pancreatic β-cell: personalizing treatment for rare forms of diabetes and hypoglycemia

Over the past 10–20 years, our understanding of the genetic etiology of monogenic disorders of the pancreatic β-cell has greatly improved. This has enabled clinicians to provide patients with more accurate information regarding prognosis and inheritance and has influenced treatment. Maturity-onset diabetes of the young and neonatal diabetes are two such examples. Patients with maturity-onset diabetes of the young due to glucokinase mutations can usually be managed by diet alone, while those affected by HNF-1α and HNF-4α mutations respond well to low doses of sulfonylureas. The identification of mutations in the ATP-dependent potassium channel genes KCNJ11 and ABCC8 as the most common cause of permanent neonatal diabetes has improved treatment regimes for affected children. In addition to enabling patients to stop insulin injections, their glycemic control has also improved. These advances show the importance of unravelling the genetics of a disease to achieve the best individualized treatment for the patients affected.

Renovascular hypertension commencing during fetal life

We report three infants with severe, early hypertension due to unilateral renovascular disease, whose cardiovascular changes, or polycythaemia, or both, indicated they had been affected as fetuses. All underwent unilateral nephrectomy, and had a similar histology, with patchy areas having relatively normal glomeruli but immature proximal tubules. This pattern may be a marker for renovascular disease in fetal life.

Exonic duplication of the hepatocyte nuclear factor-1beta gene (transcription factor 2, hepatic) as a cause of maturity onset diabetes of the young type 5

CONTEXT

Maturity onset diabetes of the young (MODY) type 5 has been described as the association of early-onset diabetes and renal disease. Actually, MODY5 encompasses multiple phenotypes, including nondiabetic progressive renal failure, kidney and genital tract malformations, atypical familial hyperuricemic nephropathy, pancreas atrophy, and liver test abnormalities. The occurrence of MODY5 has been associated with various molecular abnormalities of TCF2, including missense, nonsense, small insertion/deletions, and splice site mutations, as well as large genomic deletions or single exonic deletion of TCF2.

DESIGN

Using quantitative multiplex PCR amplification of short fluorescent fragments, we have analyzed the TCF2 gene in a French family of which three relatives presented a MODY5 phenotype. The proband had an extended clinical phenotype, including hyperuricemic nephropathy and early gout, chronic renal failure, renal morphological abnormalities, abnormal liver tests, and diabetes. His son had almost no clinical expression of the disease, whereas his grandson had a restricted but severe renal phenotype present from birth.

RESULTS

We show that a duplication of the exon 5 of TCF2 is responsible for the MODY5 phenotypes in this family.

CONCLUSIONS

Thus, we describe a novel molecular mechanism that may be responsible for MODY5, and we emphasize the wide intrafamilial variability of MODY5 expressivity. These observations suggest that the diagnosis of MODY5 may be raised even in subjects with partial phenotypes. They also confirm that quantitative multiplex PCR amplification of short fluorescent fragments analysis should be the first step of genetic screening in patients with a MODY5 phenotype.

Two variants on chromosome 17 confer prostate cancer risk, and the one in TCF2 protects against type 2 diabetes

We performed a genome-wide association scan to search for sequence variants conferring risk of prostate cancer using 1,501 Icelandic men with prostate cancer and 11,290 controls. Follow-up studies involving three additional case-control groups replicated an association of two variants on chromosome 17 with the disease. These two variants, 33 Mb apart, fall within a region previously implicated by family-based linkage studies on prostate cancer. The risks conferred by these variants are moderate individually (allele odds ratio of about 1.20), but because they are common, their joint population attributable risk is substantial. One of the variants is in TCF2 (HNF1beta), a gene known to be mutated in individuals with maturity-onset diabetes of the young type 5. Results from eight case-control groups, including one West African and one Chinese, demonstrate that this variant confers protection against type 2 diabetes.

Defining the genetic aetiology of monogenic diabetes can improve treatment

A molecular genetic diagnosis is now possible for > 80% of patients with monogenic diabetes. This not only provides accurate information regarding inheritance and prognosis, but can inform treatment decisions and improve clinical outcome. Mild fasting hyperglycaemia caused by heterozygous GCK mutations rarely requires pharmacological intervention, whereas patients with mutations in the genes encoding the transcription factors HNF-1alpha and HNF-4alpha respond well to low doses of sulphonylureas. The recent discovery that mutations in the KCNJ11 gene (encoding the Kir6.2 subunit of the K(ATP) channel) are the most common cause of permanent neonatal diabetes, has enabled children to stop insulin injections and achieve improved glycaemic control with high doses of sulphonylurea tablets. Molecular genetic testing is an essential prerequisite for the pharmacogenetic treatment of monogenic diabetes.

Neonatal cholestatic jaundice as the first symptom of a mutation in the hepatocyte nuclear factor-1beta gene (HNF-1beta)

This report describes the phenotype of a novel de novo heterozygous frameshift mutation in the hepatocyte nuclear factor-1beta gene (HNF-1beta or TCF2) manifest as a neonatal paucity of intrahepatic bile ducts. HNF-1beta mutations should be considered in neonates with cholestatic jaundice associated with renal malformation or diabetes mellitus.

Mutational analyses of UPIIIA, SHH, EFNB2 and HNF1beta in persistent cloaca and associated kidney malformations

OBJECTIVES

'Persistent cloaca' is a severe malformation affecting females in which the urinary, genital and alimentary tracts share a single conduit. Previously, a Uroplakin IIIA (UPIIIA) mutation was reported in one individual with persistent cloaca, and UPIIIA, Sonic Hedgehog (SHH), Ephrin B2 (EFNB2) and Hepatocyte Nuclear Factor 1beta (HNF1beta) are expressed during the normal development of organs that are affected in this condition. HNF1beta mutations have been associated with uterine malformations in humans, and mutations of genes homologous to human SHH or EFNB2 cause persistent cloaca in mice.

PATIENTS AND METHODS

We sought mutations of coding regions of UPIIIA, SHH, EFNB2 and HNF1beta genes by direct sequencing in a group of 20 patients with persistent cloaca. Most had associated malformations of the upper renal tract and over half had impaired renal excretory function. The majority of patients had congenital anomalies outside the renal/genital tracts and two had the VACTERL association.

RESULTS

Apart from a previously described index case, we failed to find UPIIIA mutations, and no patient had a SHH, EFNB2 or HNF1beta mutation.

CONCLUSION

Persistent cloaca is only rarely associated with UPIIIA mutation. Despite the fact that SHH and EFNB2 are appealing candidate genes, based on their expression patterns and mutant mice phenotypes, they were not mutated in these humans with persistent cloaca. Although HNF1beta mutations can perturb paramesonephric duct fusion in humans, HNF1beta was not mutated in persistent cloaca.

Anomalies of the TCF2 gene are the main cause of fetal bilateral hyperechogenic kidneys

Prenatal discovery of fetal bilateral hyperechogenic kidneys is very stressful for pregnant women and their family, and accurate diagnosis of the cause of the moderate forms of this pathology is very difficult. Hepatocyte nuclear factor-1beta that is encoded by the TCF2 gene is involved in the embryonic development of the kidneys. Sixty-two pregnancies with fetal bilateral hyperechogenic kidneys including 25 fetuses with inaccurate diagnosis were studied. TCF2 gene anomalies were detected in 18 (29%) of these 62 patients, and 15 of these 18 patients presented a complete heterozygous deletion of the TCF2 gene. Family screening revealed de novo TCF2 anomalies in more than half of the patients. TCF2 anomalies were associated with normal amniotic fluid volume and normal-sized kidneys between -2 and +2 SD in all patients except for two sisters. Antenatal cysts were detected in 11 of 18 patients, unilaterally in eight of 11. After birth, cysts appeared during the first year (17 of 18), and in patients with antenatal cysts, the number increased and developed bilaterally with decreased renal growth. In these 18 patients, the GFR decreased with longer follow-up and was lower in patients with solitary functioning dysplastic kidney. Heterozygous deletion of the TCF2 gene is an important cause of fetal hyperechogenic kidneys in this study and showed to be linked with early disease expression. The renal phenotype and the postnatal evolution were extremely variable and need a prospective long-term follow-up. Extrarenal manifestations are frequent in TCF2-linked pathologies. Therefore, prenatal counseling and follow-up should be multidisciplinary.

Hepatocyte nuclear factor-1 beta mutations cause neonatal diabetes and intrauterine growth retardation: support for a critical role of HNF-1beta in human pancreatic development

AIM

The transcription factor hepatocyte nuclear factor-1beta (HNF-1beta) is expressed in rodent pancreatic progenitor cells, where it is an important member of the genetic hierarchy that regulates the generation of pancreatic endocrine and exocrine cells. The recent description of an HNF-1beta mutation in a patient with neonatal diabetes suggests that HNF-1beta may also play a key role in human pancreatic B-cell development. We aimed to investigate the role of HNF-1beta mutations in neonatal diabetes and also the impact of HNF-1beta mutations on fetal growth.

METHODS

We sequenced the HNF-1beta gene in 27 patients with neonatal diabetes in whom other known genetic aetiologies had been excluded. Birth weight was investigated in 21 patients with HNF-1beta mutations.

RESULTS

A heterozygous HNF-1beta mutation, S148L, was identified in one patient with neonatal diabetes diagnosed at 17 days, which rapidly resolved only to relapse at 8 years. This patient had pancreatic atrophy, mild exocrine insufficiency and low birth weight (1.83 kg at 40 weeks' gestation). Intrauterine growth was markedly reduced in patients born to unaffected mothers with a median birth weight of 2.4 kg (range 1.8-3.3) (P = 0.006), median centile weight 3 (0.008-38), and 69% were small for gestational age.

CONCLUSION

HNF-1beta mutations are a rare cause of neonatal diabetes as well as pancreatic exocrine and endocrine dysfunction. Low birth weight is a common feature of patients with HNF-1beta mutations and is consistent with reduced insulin secretion in utero. These findings support a key role for HNF-1beta in early pancreatic progenitor cells in man.

Snail activation disrupts tissue homeostasis and induces fibrosis in the adult kidney

During embryonic development, the kidney epithelium originates from cells that undergo a mesenchymal to epithelial transition (MET). The reverse process, epithelium to mesenchyme transition (EMT), has been implicated in epithelial tumor progression and in the fibrosis that leads to end-stage kidney failure. Snail transcription factors induce both natural and pathological EMT, but their implication in renal development and disease is still unclear. We show that Snail genes are downregulated during the MET that occurs during renal development and that this is correlated with Cadherin-16 expression. Snail suppresses Cadherin-16 via the direct repression of the kidney differentiation factor HNF-1beta, a novel route by which Snail disrupts epithelial homeostasis. Indeed, Snail activation is sufficient to induce EMT and kidney fibrosis in adult transgenic mice. Significantly, Snail is also activated in patients with renal fibrosis. Thus, Snail expression is suppressed during renal development and it must remain silent in the mature kidney where its aberrant activation leads to fibrosis.

Alternate mRNA processing of the hepatocyte nuclear factor genes and its role in monogenic diabetes

Variation in mRNA processing has the capacity to exert fine control over gene expression in most cell types. The hepatic nuclear factor genes, like approximately 74% of the genome, produce multiple transcripts. Hepatic nuclear factor isoforms exhibit both spatial and temporal variation in expression. In this review, the known isoforms of the hepatocyte nuclear factor-1α, hepatocyte nuclear factor-1β and hepatocyte nuclear factor-4α genes are described and their properties are compared. Finally, data are discussed regarding the influence of hepatocyte nuclear factor-1α alternate mRNA processing on the clinical phenotype of maturity-onset diabetes of the young.

Mutations in the genes encoding the transcription factors hepatocyte nuclear factor 1 alpha (HNF1A) and 4 alpha (HNF4A) in maturity-onset diabetes of the young

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes mellitus characterized by autosomal dominant inheritance, early age of onset (often <25 years of age), and pancreatic beta-cell dysfunction. MODY is both clinically and genetically heterogeneous, with six different genes identified to date; glucokinase (GCK), hepatocyte nuclear factor-1 alpha (HNF1A, or TCF1), hepatocyte nuclear factor-4 alpha (HNF4A), insulin promoter factor-1 (IPF1 or PDX1), hepatocyte nuclear factor-1 beta (HNF1B or TCF2), and neurogenic differentiation 1 (NEUROD1). Mutations in the HNF1A gene are a common cause of MODY in the majority of populations studied. A total of 193 different mutations have been described in 373 families. The most common mutation is Pro291fs (P291fsinsC) in the polycytosine (poly C) tract of exon 4, which has been reported in 65 families. HNF4A mutations are rarer; 31 mutations reported in 40 families. Sensitivity to treatment with sulfonylurea tablets is a feature of both HNF1A and HNF4A mutations. The identification of an HNF1A or 4A gene mutation confirms a diagnosis of MODY and has important implications for clinical management.

Severe pancreas hypoplasia and multicystic renal dysplasia in two human fetuses carrying novel HNF1beta/MODY5 mutations

Heterozygous mutations in the HNF1beta/vHNF1/TCF2 gene cause maturity-onset diabetes of the young (MODY5), associated with severe renal disease and abnormal genital tract. Here, we characterize two fetuses, a 27-week male and a 31.5-week female, carrying novel mutations in exons 2 and 7 of HNF1beta, respectively. Although these mutations were predicted to have different functional consequences, both fetuses displayed highly similar phenotypes. They presented one of the most severe phenotypes described in HNF1beta carriers: bilateral enlarged polycystic kidneys, severe pancreas hypoplasia and abnormal genital tract. Consistent with this, we detected high levels of HNF1beta transcripts in 8-week human embryos in the mesonephros and metanephric kidney and in the epithelium of pancreas. Renal histology and immunohistochemistry analyses of mutant fetuses revealed cysts derived from all nephron segments with multilayered epithelia and dysplastic regions, accompanied by a marked increase in the expression of beta-catenin and E-cadherin. A significant proportion of cysts still expressed the cystic renal disease proteins, polycystin-1, polycystin-2, fibrocystin and uromodulin, implying that cyst formation may result from a deregulation of cell-cell adhesion and/or the Wnt/beta-catenin signaling pathway. Both fetuses exhibited a severe pancreatic hypoplasia with underdeveloped and disorganized acini, together with an absence of ventral pancreatic-derived tissue. beta-catenin and E-cadherin were strongly downregulated in the exocrine and endocrine compartments, and the islets lacked the transporter essential for glucose-sensing GLUT2, indicating a beta-cell maturation defect. This study provides evidence of differential gene-dosage requirements for HNF1beta in normal human kidney and pancreas differentiation and increases our understanding of the etiology of MODY5 disorder.

Crystallization of hepatocyte nuclear factor 1beta in complex with DNA

Hepatocyte nuclear factor 1beta (HNF1beta) is a member of the POU transcription-factor family and binds the target DNA as a dimer with nanomolar affinity. The HNF1beta-DNA complex has been prepared and crystallized by hanging-drop vapor diffusion in 6%(v/v) PEG 300, 5%(w/v) PEG 8000, 8%(v/v) glycerol and 0.1 M Tris pH 8.0. The crystals diffracted to 3.2 A (93.9% completeness) using a synchrotron-radiation source under cryogenic (100 K) conditions and belong to space group R3, with unit-cell parameters a = b = 172.69, c = 72.43 A. A molecular-replacement solution has been obtained and structure refinement is in progress. This structure will shed light on the molecular mechanism of promoter recognition by HNF1beta and the molecular basis of the disease-causing mutations found in it.

Genetics of type 2 diabetes

After several years of uncertain progress, the stage is now set for a transformation in understanding the genetic landscape of type 2 diabetes. Advances in genome informatics, genotyping technology, and statistical methodology, allied to availability of large-scale clinical material, are having a salutary effect on susceptibility gene discovery. The advent of genuinely genome-wide association scans and the prospects for combining genetics with high-throughput genomics are additional sources of optimism for the future.

Renal Phenotypes Related to Hepatocyte Nuclear Factor-1β (TCF2) Mutations in a Pediatric Cohort

The hepatocyte nuclear factor-1beta encoded by the TCF2 gene plays a role for the specific regulation of gene expression in various tissues such as liver, kidney, intestine, and pancreatic islets and is involved in the embryonic development of these organs. TCF2 mutations are known to be responsible for the maturity-onset diabetes of the young type 5 associated with renal manifestations. Several observations have suggested that TCF2 mutations may be involved in restricted renal phenotypes. Eighty children (median age at diagnosis 0.2 yr) with renal cysts, hyperechogenicity, hypoplasia, or single kidneys were studied. Quantitative multiplex PCR amplification of short fluorescence fragments for the search of large genomic rearrangements and sequencing for the detection of point mutations were performed. TCF2 anomalies were detected in one third of patients (25 of 80). The main alteration was the complete deletion of the TCF2 gene detected in 16 patients. Family screening revealed de novo TCF2 anomalies in nine of 17 probands with a high prevalence of deletions (seven of nine). TCF2 anomalies were associated with bilateral renal anomalies (P < 0.001) and bilateral cortical cysts (P < 0.001). However, abnormal renal function, detected in 40% of patients, was independent of the TCF2 genotype. No difference in renal function or severity of renal morphologic lesions was observed between patients with a TCF2 deletion and those with point mutations. In conclusion, TCF2 molecular anomalies are involved in restricted renal phenotype in childhood without alteration of glucose metabolism. These findings have important implications in the diagnosis of patients with renal dysplasia with cysts and their follow-up.