Mutations in kelch-like 3 and cullin 3 cause hypertension and electrolyte abnormalities.

Hypertension affects one billion people and is a principal reversible risk factor for cardiovascular disease. Pseudohypoaldosteronism type II (PHAII), a rare Mendelian syndrome featuring hypertension, hyperkalaemia and metabolic acidosis, has revealed previously unrecognized physiology orchestrating the balance between renal salt reabsorption and K(+) and H(+) excretion. Here we used exome sequencing to identify mutations in kelch-like 3 (KLHL3) or cullin 3 (CUL3) in PHAII patients from 41 unrelated families. KLHL3 mutations are either recessive or dominant, whereas CUL3 mutations are dominant and predominantly de novo. CUL3 and BTB-domain-containing kelch proteins such as KLHL3 are components of cullin-RING E3 ligase complexes that ubiquitinate substrates bound to kelch propeller domains. Dominant KLHL3 mutations are clustered in short segments within the kelch propeller and BTB domains implicated in substrate and cullin binding, respectively. Diverse CUL3 mutations all result in skipping of exon 9, producing an in-frame deletion. Because dominant KLHL3 and CUL3 mutations both phenocopy recessive loss-of-function KLHL3 mutations, they may abrogate ubiquitination of KLHL3 substrates. Disease features are reversed by thiazide diuretics, which inhibit the Na-Cl cotransporter in the distal nephron of the kidney; KLHL3 and CUL3 are expressed in this location, suggesting a mechanistic link between KLHL3 and CUL3 mutations, increased Na-Cl reabsorption, and disease pathogenesis. These findings demonstrate the utility of exome sequencing in disease gene identification despite the combined complexities of locus heterogeneity, mixed models of transmission and frequent de novo mutation, and establish a fundamental role for KLHL3 and CUL3 in blood pressure, K(+) and pH homeostasis.

Mutations of the catalytic subunit of RAB3GAP cause Warburg Micro syndrome.

Warburg Micro syndrome (WARBM1) is a severe autosomal recessive disorder characterized by developmental abnormalities of the eye and central nervous system and by microgenitalia. We identified homozygous inactivating mutations in RAB3GAP, encoding RAB3 GTPase activating protein, a key regulator of the Rab3 pathway implicated in exocytic release of neurotransmitters and hormones, in 12 families with Micro syndrome. We hypothesize that the underlying pathogenesis of Micro syndrome is a failure of exocytic release of ocular and neurodevelopmental trophic factors.

Phenotype and natural history in Marshall-Smith syndrome.

Marshall-Smith syndrome (MSS) is a distinctive entity of unknown etiology with fewer than 50 patients described in the medical literature to date. Through an International collaboration and use of an online wiki to facilitate data collection and sharing, we further delineate the phenotype and natural history of this syndrome. We present 15 new patients, the oldest being 30 years, provide an update on four previously published cases, and compare all patients with other patients reported in literature. Main clinical features are moderate to severe developmental delay with absent or limited speech, unusual behavior, dysharmonic bone maturation, respiratory compromise secondary to upper airway obstruction, short stature, and kyphoscoliosis. Facial features are characteristic with high forehead, underdeveloped midface, proptosis, anteverted nares, and everted lips. Minor abnormalities of brain morphology such as hypoplasia of the corpus callosum are common. Mortality from respiratory complications is high, but airway support increasingly allows survival into adulthood. Array-CGH was performed on 12 of the cohort and no copy number variants of clear clinical relevance were identified. The present study is the first reported use of an online wiki to aid delineation of a genetic syndrome, and illustrates its value in collecting detailed data in rare conditions.

Evaluation of NSD2 and NSD3 in overgrowth syndromes.

Sotos syndrome is an overgrowth condition predominantly caused by truncating mutations, missense mutations restricted to functional domains, or deletions of NSD1. NSD1 is a member of a protein family that includes NSD2 and NSD3, both of which show 70-75% sequence identity with NSD1. This strong sequence similarity suggests that abrogation of NSD2 or NSD3 function may cause non-NSD1 Sotos cases or other overgrowth phenotypes. To evaluate this hypothesis, we mutationally screened NSD2 and NSD3 in 78 overgrowth syndrome cases in which NSD1 mutations and deletions had been excluded. Additionally, we used microsatellite markers within the vicinity of the genes to look for whole gene deletions. No truncating mutations or gene deletions were identified in either gene. We identified two conservative missense NSD2 alterations in two non-Sotos overgrowth cases but neither was within a functional domain. We identified three synonymous and two intronic variants in NSD2 and two synonymous base substitutions in NSD3. Our results suggest that despite strong sequence similarity between NSD1, NSD2 and NSD3, the latter genes are unlikely to be making a substantial contribution to overgrowth phenotypes and thus may operate in distinct functional pathways from NSD1.

Genotype-phenotype associations in Sotos syndrome: an analysis of 266 individuals with NSD1 aberrations.

We identified 266 individuals with intragenic NSD1 mutations or 5q35 microdeletions encompassing NSD1 (referred to as "NSD1-positive individuals"), through analyses of 530 subjects with diverse phenotypes. Truncating NSD1 mutations occurred throughout the gene, but pathogenic missense mutations occurred only in functional domains (P < 2 x 10(-16)). Sotos syndrome was clinically diagnosed in 99% of NSD1-positive individuals, independent of the molecular analyses, indicating that NSD1 aberrations are essentially specific to this condition. Furthermore, our data suggest that 93% of patients who have been clinically diagnosed with Sotos syndrome have identifiable NSD1 abnormalities, of which 83% are intragenic mutations and 10% are 5q35 microdeletions. We reviewed the clinical phenotypes of 239 NSD1-positive individuals. Facial dysmorphism, learning disability, and childhood overgrowth were present in 90% of the individuals. However, both the height and head circumference of 10% of the individuals were within the normal range, indicating that overgrowth is not obligatory for the diagnosis of Sotos syndrome. A broad spectrum of associated clinical features was also present, the occurrence of which was largely independent of genotype, since individuals with identical mutations had different phenotypes. We compared the phenotypes of patients with intragenic NSD1 mutations with those of patients with 5q35 microdeletions. Patients with microdeletions had less-prominent overgrowth (P = .0003) and more-severe learning disability (P = 3 x 10(-9)) than patients with mutations. However, all features present in patients with microdeletions were also observed in patients with mutations, and there was no correlation between deletion size and the clinical phenotype, suggesting that the deletion of additional genes in patients with 5q35 microdeletions has little specific effect on phenotype. We identified only 13 familial cases. The reasons for the low vertical transmission rate are unclear, although familial cases were more likely than nonfamilial cases (P = .005) to carry missense mutations, suggesting that the underlying NSD1 mutational mechanism in Sotos syndrome may influence reproductive fitness.

NSD1 mutations are the major cause of Sotos syndrome and occur in some cases of Weaver syndrome but are rare in other overgrowth phenotypes.

Sotos syndrome is a childhood overgrowth syndrome characterized by a distinctive facial appearance, height and head circumference >97th percentile, advanced bone age, and developmental delay. Weaver syndrome is characterized by the same criteria but has its own distinctive facial gestalt. Recently, a 2.2-Mb chromosome 5q35 microdeletion, encompassing NSD1, was reported as the major cause of Sotos syndrome, with intragenic NSD1 mutations identified in a minority of cases. We evaluated 75 patients with childhood overgrowth, for intragenic mutations and large deletions of NSD1. The series was phenotypically scored into four groups, prior to the molecular analyses: the phenotype in group 1 (n=37) was typical of Sotos syndrome; the phenotype in group 2 (n=13) was Sotos-like but with some atypical features; patients in group 3 (n=7) had Weaver syndrome, and patients in group 4 (n=18) had an overgrowth condition that was neither Sotos nor Weaver syndrome. We detected three deletions and 32 mutations (13 frameshift, 8 nonsense, 2 splice-site, and 9 missense) that are likely to impair NSD1 functions. The truncating mutations were spread throughout NSD1, but there was evidence of clustering of missense mutations in highly conserved functional domains between exons 13 and 23. There was a strong correlation between presence of an NSD1 alteration and clinical phenotype, in that 28 of 37 (76%) patients in group 1 had NSD1 mutations or deletions, whereas none of the patients in group 4 had abnormalities of NSD1. Three patients with Weaver syndrome had NSD1 mutations, all between amino acids 2142 and 2184. We conclude that intragenic mutations of NSD1 are the major cause of Sotos syndrome and account for some Weaver syndrome cases but rarely occur in other childhood overgrowth phenotypes.

Solitary functioning kidney and diverse genital tract malformations associated with hepatocyte nuclear factor-1beta mutations.

BACKGROUND: Renal tract malformations are, on occasion, associated with uterine malformations. The transcription factor hepatocyte nuclear factor (HNF)-1beta is expressed from the earliest stages of development of the Wolffian duct, the mesonephros and metanephros, and the Müllerian ducts in the mouse. In adult mice HNF-1beta is expressed in the kidney tubules, collecting ducts, and in the oviducts and uterus in the female (Müllerian duct derivatives) and in the epididymis, vas deferens and seminal vesicles (Wolffian duct derivatives) in the male. HNF-1beta mutations have been reported in two families where affected members have renal abnormalities, female genital tract malformations and early-onset diabetes. Renal and uterine abnormalities have not been described in families without early-onset diabetes. METHODS: We sequenced the HNF-1beta gene in nine subjects with renal abnormalities and a personal or family history of female genital tract malformations, but no history of diabetes. RESULTS: Two families were identified with novel HNF-1beta mutations: a missense mutation in exon 2 with conversion of serine to proline at codon 151 (S151P) and a frameshift mutation in exon 3 with a 1 base pair deletion at codon 243 (Q243fsdelC). The S151P mutation proband has cystic kidneys and uterus didelphys. Her affected second son has renal cysts and hypospadias. The Q243fsdelC proband has a single functioning kidney and her two children have renal dysplasia. Histology in one child shows cystic dysplasia with a lack of glomeruli. The proband's sister is a mutation carrier and has a bicornuate uterus. Diabetes is not a feature in either family. CONCLUSIONS: This study confirms an association between HNF-1beta mutations and renal and Müllerian anomalies. The hypospadias may be coincidental. This study describes the first HNF-1beta mutations that are associated with a single functioning kidney and the absence of diabetes. This study further reinforces the variability of the renal and non-renal phenotypes associated with HNF-1beta mutations.