Janus-faced EPHB4-associated disorders: novel pathogenic variants and unreported intrafamilial overlapping phenotypes.

PURPOSE: Several clinical phenotypes including fetal hydrops, central conducting lymphatic anomaly or capillary malformations with arteriovenous malformations 2 (CM-AVM2) have been associated with EPHB4 (Ephrin type B receptor 4) variants, demanding new approaches for deciphering pathogenesis of novel variants of uncertain significance (VUS) identified in EPHB4, and for the identification of differentiated disease mechanisms at the molecular level. METHODS: Ten index cases with various phenotypes, either fetal hydrops, CM-AVM2, or peripheral lower limb lymphedema, whose distinct clinical phenotypes are described in detail in this study, presented with a variant in EPHB4. In vitro functional studies were performed to confirm pathogenicity. RESULTS: Pathogenicity was demonstrated for six of the seven novel EPHB4 VUS investigated. A heterogeneity of molecular disease mechanisms was identified, from loss of protein production or aberrant subcellular localization to total reduction of the phosphorylation capability of the receptor. There was some phenotype-genotype correlation; however, previously unreported intrafamilial overlapping phenotypes such as lymphatic-related fetal hydrops (LRFH) and CM-AVM2 in the same family were observed. CONCLUSION: This study highlights the usefulness of protein expression and subcellular localization studies to predict EPHB4 variant pathogenesis. Our accurate clinical phenotyping expands our interpretation of the Janus-faced spectrum of EPHB4-related disorders, introducing the discovery of cases with overlapping phenotypes.

Syndromic disorders caused by gain-of-function variants in KCNH1, KCNK4, and KCNN3-a subgroup of K+ channelopathies.

Decreased or increased activity of potassium channels caused by loss-of-function and gain-of-function (GOF) variants in the corresponding genes, respectively, underlies a broad spectrum of human disorders affecting the central nervous system, heart, kidney, and other organs. While the association of epilepsy and intellectual disability (ID) with variants affecting function in genes encoding potassium channels is well known, GOF missense variants in K+ channel encoding genes in individuals with syndromic developmental disorders have only recently been recognized. These syndromic phenotypes include Zimmermann-Laband and Temple-Baraitser syndromes, caused by dominant variants in KCNH1, FHEIG syndrome due to dominant variants in KCNK4, and the clinical picture associated with dominant variants in KCNN3. Here we review the presentation of these individuals, including five newly reported with variants in KCNH1 and three additional individuals with KCNN3 variants, all variants likely affecting function. There is notable overlap in the phenotypic findings of these syndromes associated with dominant KCNN3, KCNH1, and KCNK4 variants, sharing developmental delay and/or ID, coarse facial features, gingival enlargement, distal digital hypoplasia, and hypertrichosis. We suggest to combine the phenotypes and define a new subgroup of potassium channelopathies caused by increased K+ conductance, referred to as syndromic neurodevelopmental K+ channelopathies due to dominant variants in KCNH1, KCNK4, or KCNN3.

A dyadic approach to the delineation of diagnostic entities in clinical genomics.

The delineation of disease entities is complex, yet recent advances in the molecular characterization of diseases provide opportunities to designate diseases in a biologically valid manner. Here, we have formalized an approach to the delineation of Mendelian genetic disorders that encompasses two distinct but inter-related concepts: (1) the gene that is mutated and (2) the phenotypic descriptor, preferably a recognizably distinct phenotype. We assert that only by a combinatorial or dyadic approach taking both of these attributes into account can a unitary, distinct genetic disorder be designated. We propose that all Mendelian disorders should be designated as "GENE-related phenotype descriptor" (e.g., "CFTR-related cystic fibrosis"). This approach to delineating and naming disorders reconciles the complexity of gene-to-phenotype relationships in a simple and clear manner yet communicates the complexity and nuance of these relationships.

Maternally inherited 133kb deletion of 14q32 causing Kagami-Ogata syndrome.

We present a case of a newborn female with multiple anomalies demonstrating that the causes of imprinting disorders rely not only on the parent-of-origin of the chromosomal aberrations, but also the scope of genes contained in the imprinted region. The newborn female presented with prenatal polyhydramnios, neonatal respiratory distress, distal contractures, abdominal hernia, bell-shaped thorax, and abnormal ribs. The neonate required mechanical ventilation due to apnea, underwent surgery for laryngomalacia, and showed development delay by age 11 months. Chromosomal microarray analysis identified a single copy number loss in chromosome region 14q32.2q32.31, containing genes that are differentially expressed based on parent-of-origin. Microarray analysis also confirmed the identical deletion in the patient's mother, who was reported to be normal. Additional molecular analyses determined the exact size and breakpoints of the deletion as well as methylation states in both the patient and her mother. The maternally transmitted deletion was responsible for Kagami-Ogata syndrome in the patient.

Ehlers-Danlos syndrome hypermobility type is associated with rheumatic diseases.

We retrospectively analyzed electronic medical records of patients with Ehlers-Danlos Syndrome hypermobility type (HEDS), including demographic information, workup, rheumatological diagnoses in order to determine its association with rheumatological conditions. HEDS Patients were stratified according to level of workup received (no additional work (physical exam only) = NWU, limited workup = LWU, comprehensive workup = CWU)). HEDS patients were predominantly female (21:4, F:M). The percentage of patients with at least one rheumatological condition was significantly correlated with level of workup (NWU, 9.2%; LWU, 33.3%, CWU, 67.1%; p-value < 0.0001). The HLA-B27 antigen was more prevalent (p-value < 2.2 × 10-8) in the CWU HEDS patients (23.9%) than in the general population of the United States (6.1%). HEDS with CWU were associated with more rheumatological conditions (i.e. psoriasis, ankylosing spondylitis, rheumatoid arthritis, fibromyalgia) than those with NWU or LWU. In conclusion, HEDS is associated with complicated rheumatological conditions, which are uncovered by comprehensive workup. These conditions require different clinical management strategies than HEDS, and left untreated could contribute to the pain or even physical disability (i.e. joint erosions) in HEDS patients. While the mechanisms underlying these associations are unknown, it is important that all HEDS patients receive adequate workup to ensure a complete clinical understanding for the best care strategy possible.

Improving genetic health care: a Northern New England pilot project addressing the genetic evaluation of the child with developmental delays or intellectual disability.

In 2006, all clinical genetics practices in Northern New England (Vermont, New Hampshire, and Maine) formed a learning collaborative with the purpose of improving genetic health care and outcomes. This article describes the current status of this effort. The methodology is based on our own modifications of the Institute of Healthcare Improvement "Breakthrough Series" and the Northern New England Cystic Fibrosis Consortium. Because of similarities across practices and the availability of existing published practice parameters, the clinical genetics evaluation of the child with developmental delay or intellectual disability was chosen as the topic to be studied. The aim was to improve the rate of etiological diagnosis of those with developmental delays referred to each genetics center by improving the processes of care. Process and outcomes were evaluated. Four of five sites also evaluated the impact of array comparative genomic hybridization (a-CGH) laboratory testing of such patients. There was significant site-to-site variation in the rate of new diagnoses by a-CGH with the average new diagnosis rate of 11.8% (range 5.4-28.8%). Barriers to implementation of the process and outcome data collection and analysis were significant and related to time pressures, lack of personnel or staff to support this activity, and competing quality improvement initiatives at the institutional home of some genetics centers.

Molecular and clinical analyses of Greig cephalopolysyndactyly and Pallister-Hall syndromes: robust phenotype prediction from the type and position of GLI3 mutations.

Mutations in the GLI3 zinc-finger transcription factor gene cause Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS), which are variable but distinct clinical entities. We hypothesized that GLI3 mutations that predict a truncated functional repressor protein cause PHS and that functional haploinsufficiency of GLI3 causes GCPS. To test these hypotheses, we screened patients with PHS and GCPS for GLI3 mutations. The patient group consisted of 135 individuals: 89 patients with GCPS and 46 patients with PHS. We detected 47 pathological mutations (among 60 probands); when these were combined with previously published mutations, two genotype-phenotype correlations were evident. First, GCPS was caused by many types of alterations, including translocations, large deletions, exonic deletions and duplications, small in-frame deletions, and missense, frameshift/nonsense, and splicing mutations. In contrast, PHS was caused only by frameshift/nonsense and splicing mutations. Second, among the frameshift/nonsense mutations, there was a clear genotype-phenotype correlation. Mutations in the first third of the gene (from open reading frame [ORF] nucleotides [nt] 1-1997) caused GCPS, and mutations in the second third of the gene (from ORF nt 1998-3481) caused primarily PHS. Surprisingly, there were 12 mutations in patients with GCPS in the 3' third of the gene (after ORF nt 3481), and no patients with PHS had mutations in this region. These results demonstrate a robust correlation of genotype and phenotype for GLI3 mutations and strongly support the hypothesis that these two allelic disorders have distinct modes of pathogenesis.

Connexin 43 (GJA1) mutations cause the pleiotropic phenotype of oculodentodigital dysplasia.

Gap junctions are assemblies of intercellular channels that regulate a variety of physiologic and developmental processes through the exchange of small ions and signaling molecules. These channels consist of connexin family proteins that allow for diversity of channel composition and conductance properties. The human connexin 43 gene, or GJA1, is located at human chromosome 6q22-q23 within the candidate region for the oculodentodigital dysplasia locus. This autosomal dominant syndrome presents with craniofacial (ocular, nasal, and dental) and limb dysmorphisms, spastic paraplegia, and neurodegeneration. Syndactyly type III and conductive deafness can occur in some cases, and cardiac abnormalities are observed in rare instances. We found mutations in the GJA1 gene in all 17 families with oculodentodigital dysplasia that we screened. Sixteen different missense mutations and one codon duplication were detected. These mutations may cause misassembly of channels or alter channel conduction properties. Expression patterns and phenotypic features of gja1 animal mutants, reported elsewhere, are compatible with the pleiotropic clinical presentation of oculodentodigital dysplasia.