A zebrafish model of foxe3 deficiency demonstrates lens and eye defects with dysregulation of key genes involved in cataract formation in humans.

The Forkhead box E3 (FOXE3) gene encodes a transcription factor with a forkhead/winged helix domain that is critical for development of the lens and anterior segment of the eye. Monoallelic and biallelic deleterious sequence variants in FOXE3 cause aphakia, cataracts, sclerocornea and microphthalmia in humans. We used clustered regularly interspaced short palindromic repeats/Cas9 injections to target the foxe3 transcript in zebrafish in order to create an experimental model of loss of function for this gene. Larvae that were homozygous for an indel variant, c.296_300delTGCAG, predicting p.(Val99Alafs*2), demonstrated severe eye defects, including small or absent lenses and microphthalmia. The lenses of the homozygous foxe3 indel mutants showed more intense staining with zl-1 antibody compared to control lenses, consistent with increased lens fiber cell differentiation. Whole genome transcriptome analysis (RNA-Seq) on RNA isolated from wildtype larvae and larvae with eye defects that were putative homozygotes for the foxe3 indel variant found significant dysregulation of genes expressed in the lens and eye whose orthologues are associated with cataracts in human patients, including cryba2a, cryba1l1, mipa and hsf4. Comparative analysis of this RNA-seq data with iSyTE data identified several lens-enriched genes to be down-regulated in foxe3 indel mutants. We also noted upregulation of lgsn and crygmxl2 and downregulation of fmodb and cx43.4, genes that are expressed in the zebrafish lens, but that are not yet associated with an eye phenotype in humans. These findings demonstrate that this new zebrafish foxe3 mutant model is highly relevant to the study of the gene regulatory networks conserved in vertebrate lens and eye development.

Correction to: A zebrafish model of foxe3 deficiency demonstrates lens and eye defects with dysregulation of key genes involved in cataract formation in humans.

The authors noticed that Fig. 5A and B aspect ratios appeared sub-optimal in the online published version. This has now been changed.

Exome sequencing in 32 patients with anophthalmia/microphthalmia and developmental eye defects.

Anophthalmia/microphthalmia (A/M) is a genetically heterogeneous birth defect for which the etiology is unknown in more than 50% of patients. We used exome sequencing with the ACE Exome(TM) (Personalis, Inc; 18 cases) and UCSF Genomics Core (21 cases) to sequence 28 patients with A/M and four patients with varied developmental eye defects. In the 28 patients with A/M, we identified de novo mutations in three patients (OTX2, p.(Gln91His), RARB, p.Arg387Cys and GDF6, p.Ala249Glu) and inherited mutations in STRA6 in two patients. In patients with developmental eye defects, a female with cataracts and cardiomyopathy had a de novo COL4A1 mutation, p.(Gly773Arg), expanding the phenotype associated with COL4A1 to include cardiomyopathy. A male with a chorioretinal defect, microcephaly, seizures and sensorineural deafness had two PNPT1 mutations, p.(Ala507Ser) and c.401-1G>A, and we describe eye defects associated with this gene for the first time. Exome sequencing was efficient for identifying mutations in pathogenic genes for which there is no clinical testing available and for identifying cases that expand phenotypic spectra, such as the PNPT1 and COL4A1-associated disorders described here.

Sequence variants in the HLX gene at chromosome 1q41-1q42 in patients with diaphragmatic hernia.

Congenital diaphragmatic hernia (CDH) is a common birth defect for which few causative genes have been identified. Several candidate regions containing genes necessary for normal diaphragm development have been identified, including a 4-5 Mb deleted region at chromosome 1q41-1q42 from which the causative gene(s) has/have not been cloned. We selected the HLX gene from this interval as a candidate gene for CDH, as the Hlx homozygous null mouse has been reported to have diaphragmatic defects and the gene was described as being expressed in the murine diaphragm. We re-sequenced HLX in 119 CDH patients and identified four novel single nucleotide substitutions that predict amino acid changes: p.S12F, p.S18L, p.D173Y and p.A235V. These sequence alterations were all present in patients with isolated CDH, although patients with both isolated CHD and CDH with additional anomalies were studied. The single-nucleotide substitutions were absent in more than 186 control chromosomes. In-situ hybridization studies confirmed expression of Hlx in the developing murine diaphragm at the site of the junction of the diaphragm and the liver. Although functional studies to determine if these novel sequence variants altered the inductive activity of Hlx on the alpha-smooth muscle actin and SM22alpha promoters showed no significant differences between the variants and wild-type Hlx, sequence variants in HLX may still be relevant in the pathogenesis of CDH in combination with additional genetic and environmental factors.

Subtypes of frontonasal dysplasia are useful in determining clinical prognosis.

Frontonasal dysplasia [FND; OMIM 136760] results from abnormal morphogenesis of the frontonasal process with disruption of the formation of the facial midline. Craniofacial anomalies in FND include anterior cranium bifidum, ocular hypertelorism, orofacial clefting and notching or clefting of the alae nasi. The majority of FND cases are sporadic and discordance has been demonstrated in monozygotic twin pairs, arguing against a strong inherited component in pathogenesis. However, pedigrees with Mendelian inheritance and non-recurrent chromosome aberrations in FND patients demonstrate that gene mutations or cytogenetic imbalance can also be important in the etiology of this phenotype. We classified 101 reported cases of FND from the medical literature and three new cases into seven separate FND phenotypic subtypes in addition to isolated FND. Our aim was to evaluate FND patients for distinct phenotypes within the FND spectrum and to determine the evidence for a genetic etiology in each of the different subtypes. Our analysis showed significant differences in the severity of the accompanying malformations and the rates of learning disabilities in the FND subtypes, although the small patient numbers and method of patient ascertainment may have influenced the data. The results suggest that cases with FND should be evaluated for additional anomalies, as these may help to determine prognosis.

Candidate genes for congenital diaphragmatic hernia from animal models: sequencing of FOG2 and PDGFRalpha reveals rare variants in diaphragmatic hernia patients.

Congenital diaphragmatic hernia (CDH) is a common, life threatening birth defect. Although there is strong evidence implicating genetic factors in its pathogenesis, few causative genes have been identified, and in isolated CDH, only one de novo, nonsense mutation has been reported in FOG2 in a female with posterior diaphragmatic eventration. We report here that the homozygous null mouse for the Pdgfralpha gene has posterolateral diaphragmatic defects and thus is a model for human CDH. We hypothesized that mutations in this gene could cause human CDH. We sequenced PDGFRalpha and FOG2 in 96 patients with CDH, of which 53 had isolated CDH (55.2%), 36 had CDH and additional anomalies (37.5%), and 7 had CDH and known chromosome aberrations (7.3%). For FOG2, we identified novel sequence alterations predicting p.M703L and p.T843A in two patients with isolated CDH that were absent in 526 and 564 control chromosomes respectively. These altered amino acids were highly conserved. However, due to the lack of available parental DNA samples we were not able to determine if the sequence alterations were de novo. For PDGFRalpha, we found a single variant predicting p.L967V in a patient with CDH and multiple anomalies that was absent in 768 control chromosomes. This patient also had one cell with trisomy 15 on skin fibroblast culture, a finding of uncertain significance. Although our study identified sequence variants in FOG2 and PDGFRalpha, we have not definitively established the variants as mutations and we found no evidence that CDH commonly results from mutations in these genes.

KBG syndrome: report of twins, neurological characteristics, and delineation of diagnostic criteria.

KBG syndrome is a multiple congenital anomaly (MCA) syndrome comprising developmental delay, postnatal short stature, and delayed bone age. Many physical anomalies involving the face, hands, and costovertebral axis have been described in this syndrome. We present twin males with KBG syndrome and a review of 50 published case reports, with particular emphasis on the neurological aspects of KBG syndrome, including seizures, MRI findings, and behavior difficulties. It is argued that diagnostic criteria for KBG syndrome should include neurological involvement, that is, global developmental delay, seizures, and/or mental retardation (MR). The characteristic facial changes and representative hand and costovertebral anomalies are also defined. These diagnostic criteria were obtained from 50 publications and appeared to support the diagnosis in 43 cases. They will be helpful to pediatricians, geneticists, and neurologists in evaluating patients for this condition.

Genomic microarray analysis identifies candidate loci in patients with corpus callosum anomalies.

Absence of the corpus callosum is often associated with cognitive deficits, autism, and epilepsy. Using a genomic microarray, the authors analyzed DNA from 25 patients with radiographically confirmed callosal anomalies and identified three patients with de novo copy number changes in chromosome regions 2q37, 6qter, and 8p. Chromosomal deletions and duplications may be a relatively common cause of cerebral malformations.

Fraser syndrome and cryptophthalmos: review of the diagnostic criteria and evidence for phenotypic modules in complex malformation syndromes.

Fraser syndrome is characterised by cryptophthalmos, cutaneous syndactyly, malformations of the larynx and genitourinary tract, craniofacial dysmorphism, orofacial clefting, mental retardation, and musculoskeletal anomalies. The inheritance is autosomal recessive. No diagnostic cytogenetic abnormalities have been documented in affected patients, and no molecular genetic studies have been reported. We have reviewed 117 cases diagnosed as Fraser syndrome or cryptophthalmos published since the comprehensive review of Thomas et al in 1986 in order to validate the published diagnostic criteria and to delineate the phenotype associated with this syndrome. Our series showed more females (57/117) than males and consanguinity was present in 29/119 (24.8%). Eighty-eight patients satisfied the diagnostic criteria for Fraser syndrome (75%). Cryptophthalmos was present in 103/117 (88%), syndactyly in 72/117 (61.5%), and ambiguous genitalia in 20/117 (17.1%). Ear malformations were recorded in 69/117 (59%), and renal agenesis in 53/117 (45.3%). Use of the published diagnostic criteria excluded several patients with cryptophthalmos and one or more physical feature(s) consistent with Fraser syndrome. The frequency of additional anomalies in our series was also higher than previously reported (for example, imperforate anus or anal stenosis were found in 34/117 (29%) compared with 2/124 (2%) in the series of Thomas et al (1986) and choanal stenosis or atresia was present in 7/117 (6%) compared to 0/124. These findings emphasise the clinical variability associated with Fraser syndrome and support genetic heterogeneity of the syndrome. We also noted patterns of anomalies (for example, bicornuate uterus with imperforate anus or anal stenosis and renal malformations) that are found in other syndromes and associations without cryptophthalmos, suggesting that common modifier genes may explain some of the phenotypic variation in Fraser syndrome.

Mutation analysis of the MKKS gene in McKusick-Kaufman syndrome and selected Bardet-Biedl syndrome patients.

McKusick-Kaufman syndrome comprises hydrometrocolpos, polydactyly, and congenital heart defects and overlaps with Bardet-Biedl syndrome, comprising retinitis pigmentosa, polydactyly, obesity, mental retardation, and renal and genital anomalies. Bardet-Biedl syndrome is genetically heterogeneous with three cloned genes ( BBS2, BBS4, and MKKS) and at least three other known loci ( BBS1, BBS3, and BBS5). Both McKusick-Kaufman syndrome and Bardet-Biedl syndrome are inherited in an autosomal recessive pattern, and both syndromes are caused by mutations in the MKKS gene. However, mutations in MKKS are found in only 4%-11% of unselected Bardet-Biedl syndrome patients. We hypothesized that an analysis of patients with atypical Bardet-Biedl syndrome and McKusick-Kaufman syndrome (Group I; 15 probands) and patients with Bardet-Biedl syndrome who had linkage results inconsistent with linkage to the other loci (Group II; 12 probands) could increase the MKKS mutation yield. Both mutant alleles were identified in only two families in Group II. Single (heterozygous) sequence variations were found in three Group I families and in two Group II families. Combining these results with previously published data showed that only one mutant allele was detected in nearly half of all patients screened to date, suggesting that unusual mutational mechanisms or patterns of inheritance may be involved. However, sequencing of the BBS2 gene in these patients did not provide any evidence of digenic or "triallelic" inheritance. The frequency of detected mutations in MKKS in Group II patients was 24%, i.e., six times higher than the published rate for unselected BBS patients, suggesting that small-scale linkage analyses may be useful in suitable families.

Unfolding the role of chaperones and chaperonins in human disease.

Molecular chaperones comprise several highly conserved families of related proteins, many of which are also heat shock proteins. Chaperone proteins are crucial for the maintenance of native protein conformation and recent research has demonstrated several mechanisms where defective chaperone proteins have pathogenic consequences. In this article, we describe the structure and function of chaperones in bacterial and eukaryotic cells, focusing on the chaperonin class of chaperones. We then summarize contemporary research concerning the role of these proteins in several human diseases, concentrating on the genes coding for chaperone and chaperonin proteins and the importance of chaperones in neurodegenerative diseases and as modifiers of amino acid substitution mutations in other proteins.

Phenotypic overlap of McKusick-Kaufman syndrome with bardet-biedl syndrome: a literature review.

Hydrometrocolpos (HMC) and post-axial polydactyly (PAP) are common to both McKusick-Kaufman syndrome (MKS) and Bardet-Biedl syndrome (BBS). We review reported cases of MKS and BBS presenting with HMC and PAP early in life to determine if there are clinical features that allow discrimination between the two syndromes as the primary features of retinitis pigmentosa, obesity, learning disability in BBS are age-dependent. We did not find any phenotypic features that allowed reliable differentiation between the two syndromes in the neonatal period. However, uterine, ovarian, and fallopian tube anomalies are more common in BBS patients, and it may be that these clinical features prove to be useful discriminating features. We conclude that sporadic female infants with HMC and PAP cannot be diagnosed with MKS until at least age 5 years and that monitoring for the complications of BBS should be performed in these patients.

Mutations in MKKS cause Bardet-Biedl syndrome.

Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder with locus heterogeneity. None of the 'responsible' genes have previously been identified. Some BBS cases (approximately 10%) remain unassigned to the five previously mapped loci. McKusick-Kaufma syndrome (MKS) includes hydrometrocolpos, postaxial polydactyly and congenital heart disease, and is also inherited in an autosomal recessive manner. We ascertained 34 unrelated probands with classic features of BBS including retinitis pigmentosa (RP), obesity and polydactyly. The probands were from families unsuitable for linkage because of family size. We found MKKS mutations in four typical BBS probands (Table 1). The first is a 13-year-old Hispanic girl with severe RP, PAP, mental retardation and obesity (BMI >40). She was a compound heterozygote for a missense (1042GA, G52D) and a nonsense (1679TA, Y264stop) mutation in exon 3. Cloning and sequencing of the separate alleles confirmed that the mutations were present in trans. A second BBS proband (from Newfoundland), born to consanguineous parents, was homozygous for two deletions (1316delC and 1324-1326delGTA) in exon 3, predicting a frameshift. An affected brother was also homozygous for the deletions, whereas an unaffected sibling had two normal copies of MKKS. Both the proband and her affected brother had RP, PAP, mild mental retardation, morbid obesity (BMI >50 and 37, respectively), lobulated kidneys with prominent calyces and diabetes mellitus (diagnosed at ages 33 and 30, respectively). A deceased sister (DNA unavailable) had similar phenotypic features (RP with blindness by age 13, BMI >45, abnormal glucose tolerance test and IQ=64, vaginal atresia and syndactyly of both feet). Both parents and the maternal grandfather were heterozygous for the deletions. Genotyping with markers from the MKKS region confirmed homozygosity at 20p12 in both affected individuals.

Sudden death caused by pulmonary thromboembolism in Proteus syndrome.

We report 3 patients with Proteus syndrome (PS) who died suddenly from pulmonary embolism (PE). The first patient was a male diagnosed with PS at 12 years who had varicose veins, portal vein thrombosis, right iliac vein occlusion and recurrent PE. At age 25 years, he was admitted to the hospital with a severe headache. Despite therapeutic doses of warfarin, investigations for an acute episode of breathlessness showed PE and he was unable to be resuscitated. The second case was a 9-year-old male with PS who collapsed at home and could not be revived. Autopsy revealed that the cause of death was a PE associated with thrombosis of the deep veins (DVT). The third patient was a 17-year-old female undergoing inpatient treatment for sinusitis when she unexpectedly arrested. She could not be revived and a full autopsy revealed a large PE with no identified DVT. We conclude that PE is a serious complication of PS and recommend vigilance concerning the signs and symptoms of thrombosis and PE in individuals with PS, including children. Aggressive evaluation and treatment should be considered urgently in patients with PS and signs or symptoms of DVT.

ACTH receptor mutation in a girl with familial glucocorticoid deficiency.

Familial glucocorticoid deficiency (FGD) has long been recognised as a clinical entity, but molecular studies have so far been performed in only a few individuals. We describe a girl born to consanguineous Pakistani parents with clinical and biochemical features of FGD who is homozygous for the R146H mutation of the adrenocorticotropic hormone (ACTH) receptor gene. This mutation creates a new restriction enzyme site in the ACTH receptor gene, allowing accurate characterisation of the mutation without DNA sequencing. Our patient is the third child reported to be homozygous for the R146H mutation. Interestingly, she has a tall stature, a clinical finding reported in several children who have ACTH insufficiency and mutations of the ACTH receptor gene. We suggest that mutation analysis of the ACTH receptor gene be considered in children with clinical features of FGD and tall stature.

Interstitial deletion of band 3q25.

Interstitial deletions of the long arm of chromosome 3 are rare. We report a man with an interstitial deletion involving band 3q25. To our knowledge, this is the first patient to be described with this cytogenetic abnormality.