Histone lysine methyltransferases (KMTs) and demethylases (KDMs) underpin gene regulation. Here we demonstrate that variants causing haploinsufficiency of KMTs and KDMs are frequently encountered in individuals with developmental disorders. Using a combination of human variation databases and existing animal models, we determine 22 KMTs and KDMs as additional candidates for dominantly inherited developmental disorders. We show that KMTs and KDMs that are associated with, or are candidates for, dominant developmental disorders tend to have a higher level of transcription, longer canonical transcripts, more interactors, and a higher number and more types of post-translational modifications than other KMT and KDMs. We provide evidence to firmly associate KMT2C, ASH1L, and KMT5B haploinsufficiency with dominant developmental disorders. Whereas KMT2C or ASH1L haploinsufficiency results in a predominantly neurodevelopmental phenotype with occasional physical anomalies, KMT5B mutations cause an overgrowth syndrome with intellectual disability. We further expand the phenotypic spectrum of KMT2B-related disorders and show that some individuals can have severe developmental delay without dystonia at least until mid-childhood. Additionally, we describe a recessive histone lysine-methylation defect caused by homozygous or compound heterozygous KDM5B variants and resulting in a recognizable syndrome with developmental delay, facial dysmorphism, and camptodactyly. Collectively, these results emphasize the significance of histone lysine methylation in normal human development and the importance of this process in human developmental disorders. Our results demonstrate that systematic clinically oriented pathway-based analysis of genomic data can accelerate the discovery of rare genetic disorders.

The Loeys–Dietz syndrome (LDS) is a connective tissue disorder affecting the cardiovascular, skeletal, and ocular system. Most typically, LDS patients present with aortic aneurysms and arterial tortuosity, hypertelorism, and bifid/broad uvula or cleft palate. Initially, mutations in transforming growth factor‐β (TGF‐β) receptors (TGFBR1 and TGFBR2) were described to cause LDS, hereby leading to impaired TGF‐β signaling. More recently, TGF‐β ligands, TGFB2 and TGFB3, as well as intracellular downstream effectors of the TGF‐β pathway, SMAD2 and SMAD3, were shown to be involved in LDS. This emphasizes the role of disturbed TGF‐β signaling in LDS pathogenesis. Since most literature so far has focused on TGFBR1/2, we provide a comprehensive review on the known and some novel TGFB2/3 and SMAD2/3 mutations. For TGFB2 and SMAD3, the clinical manifestations, both of the patients previously described in the literature and our newly reported patients, are summarized in detail. This clearly indicates that LDS concerns a disorder with a broad phenotypical spectrum that is still emerging as more patients will be identified. All mutations described here are present in the corresponding Leiden Open Variant Database.

Dominant optic atrophy (DOA) is the commonest form of inherited optic neuropathy. Although heterogeneous, a major locus has been mapped to chromosome 3q28 and the gene responsible, OPA1, was recently identified. We therefore screened a panel of 35 DOA patients for mutations in OPA1. This revealed 14 novel mutations and a further three known mutations, which together accounted for 20 of the 35 families (57%) included in this study. This more than doubles the number of OPA1 mutations reported in the literature, bringing the total to 25. These are predominantly null mutations generating truncated proteins, strongly suggesting that the mechanism underlying DOA is haploinsufficiency. The mutations are largely family-specific, although a common 4 bp deletion in exon 27 (eight different families) and missense mutations in exons 8 (two families) and 9 (two families) have been identified. Haplotype analysis of individuals with the exon 27 2708del(TTAG) mutation suggests that this is a mutation hotspot and not an ancient mutation, thus excluding a major founder effect at the OPA1 locus. The mutation screening in this study also identified a number of asymptomatic individuals with OPA1 mutations. A re-calculation of the penetrance of this disorder within two of our families indicates figures as low as 43 and 62% associated with the 2708del(TTAG) mutation. If haploinsufficiency is the mechanism underlying DOA it is unlikely that this figure will be mutation-specific, indicating that the penetrance in DOA is much lower than the 98% reported previously. To investigate whether Leber's hereditary optic neuropathy (LHON) could be caused by mutations in OPA1 we also screened a panel of 28 LHON patients who tested negatively for the three major LHON mutations. No mutations were identified in any LHON patients, indicating that DOA and LHON are genetically distinct.

We recently reported SMARCE1 mutations as a cause of spinal clear cell meningiomas. Here, we have identified five further cases with non-NF2 spinal meningiomas and six with non-NF2 cranial meningiomas. Three of the spinal cases and three of the cranial cases were clear cell tumours. We screened them for SMARCE1 mutations and investigated copy number changes in all point mutation-negative samples. We identified two novel mutations in individuals with spinal clear cell meningiomas and three mutations in individuals with cranial clear cell meningiomas. Copy number analysis identified a large deletion of the 5' end of SMARCE1 in two unrelated probands with spinal clear cell meningiomas. Testing of affected and unaffected relatives of one of these individuals identified the same deletion in two affected female siblings and their unaffected father, providing further evidence of incomplete penetrance of meningioma disease in males. In addition, we found loss of SMARCE1 protein in three of 10 paraffin-embedded cranial clear cell meningiomas. Together, these results demonstrate that loss of SMARCE1 is relevant to cranial as well as spinal meningiomas. Our study broadens the spectrum of mutations in the SMARCE1 gene and expands the phenotype to include cranial clear cell meningiomas.

A large family with autosomal dominant segregation of presenile dementia, and other neurological and behavioural features is described. At various times, family members have carried diagnoses of Alzheimer's disease, Huntington's disease, Parkinson's disease, myoclonic epilepsy, atypical dementia, Pick's disease, Creutzfeldt-Jakob disease and Gerstmann-Sträussler syndrome. Molecular genetic studies have enabled classification of this disease at the molecular level as one of the group of inherited prion diseases. Here we describe the phenotype of inherited prion disease (PrP 144 bp insertion).

Genealogical and molecular studies were carried out in four families in which early onset dementia is inherited as an autosomal dominant. These studies indicated that the four families derive from four siblings whose parents were born in the late 18th century in South-East England. The disease was found to be closely linked to a 144 bp insertion within the open reading frame of the prion protein (PrP) gene with a maximum LOD score of 11.02 at zero recombination. Within the general population the PrP gene is polymorphic at codon 129 (allele frequency approximately 30% valine, 70% methionine). The insertion in this family is always within a methionine-129 allele. The age at death of affected individuals whose normal allele encoded methionine at codon 129 was significantly lower than those whose normal allele encoded valine. The clinical features which were very variable and the neuropathological findings, which sometimes included spongiform encephalopathy, but which often did not, are described fully in the accompanying article (Collinge et al., 1992).

We report a case of a female infant with a de novo deletion of the short arm of chromosome 9, sex reversal, and an apparently intact SRY gene. Sex reversal has been reported in a number of subjects with a normal Y chromosome and a deletion of the terminal segment of the short arm of chromosome 9. The factors controlling early development of the male testes are unknown. There are likely to be many genes involved and we present additional evidence that one of these is situated on the end of the short arm of chromosome 9. (J Med Genet 1993;30:518-20) The primary event in the determination of male and female sex is dependent on the presence or absence of the sex determining region of the Y chromosome (SRY).1 Sex reversal has been reported in a number of subjects with a Y chromosome and a terminal deletion of the short arm of chromosome 9.2-6 These cases involved translocation of chromosome 9 with other chromosomes and therefore they were trisomic for part of another chromosome in addition to being monosomic for terminal 9p. We report a case of a sex reversed female infant with a de novo deletion of the distal short arm of chromosome 9, sex reversal, and an apparently intact SRY gene. Figure 1 Partial G banded metaphase to show deleted chromosome 9 with apparently terminal deletion of the short arm del (9) (p2305). Frozen fibroblasts from the proband are banked at Guy's Hospital, reference 90/3077.The SRY gene was amplified by the polymerase chain reaction, cloned, and sequenced and no mutations found.' Endocrine investigations Endocrine investigation was consistent with gonadal failure with a raised FSH of > 40 mU/l (normal range < 2 mU/l). The LH rose markedly after LHRH stimulation from 11 IU/l to > 50 IU/l (resting normal range 1-6 IU/1). The testosterone rose only minimally from 0*9 to 1-5 nmol/l (resting normal range A1Onmol/l) after three injections of HCG (1000 units x 3).~~- Docherty, Robb, Ramani, Hawkins, Grant Summary of patients with sex reversal and deletions of the distal short arm of chromosome 9.

A fetus is described with anophthalmia, absent pituitary, hypoplastic adrenal glands and kidneys, absent left horn of the uterus, underdeveloped genitalia, and clinodactyly, with a deletion of 14(q22q23). A review of published reports found no similar deletion cases.Although deletions of small chromosomal segments are relatively common, there are only a few instances reported of deletions involving the long arm of chromosome 14. Furthermore, most of these are terminal; there appear to be only four published cases of interstitial deletions. [1][2][3] We describe a fetus with an interstitial deletion of 14q and an unusual combination of clinical features.Case report This was the fourth pregnancy ofunrelated Caucasians, the mother and father being 31 and 29 years old, respectively. The first pregnancy was ectopic, the second ended as a spontaneous abortion at 12 weeks, and the third resulted in a normal appearing stillbirth at 22 weeks owing to placenta praevia. In the fourth pregnancy, ultrasound examination at 21 weeks showed an unusually shaped fetal head, small orbits with the absence of eye lenses, loose skin at the back of the neck, and possible polydactyly. In view of these findings, the couple opted for termination of the pregnancy.The female fetus was markedly dysmorphic (figure). There was bilateral anophthalmia, confirmed by histology, and short, widely spaced palpebral