Prenatal counselling regarding prognosis and risk of chromosomal defects should be tailored to cleft category, and more importantly to the presence/absence of associated anomalies. Irrespective of cleft category, clinicians should advise invasive genetic testing if associated anomalies are seen prenatally. In the absence of associated anomalies, prenatal conventional karyotyping is not recommended in CL, although array comparative genomic hybridisation should be considered. In presumed isolated CLP or CP, prenatal invasive testing, preferably by array based methods, is recommended.

Tooth agenesis is one of the most common developmental anomalies in man. Oligodontia, a severe form of tooth agenesis, occurs both as an isolated anomaly and as a syndromal feature. We performed exome sequencing on 20 unrelated individuals with apparent non-syndromic oligodontia and failed to detect mutations in genes previously associated with oligodontia. In three of the probands, we detected heterozygous variants in LRP6, and sequencing of additional oligodontia-affected individuals yielded one additional mutation in LRP6. Three mutations (c.1144_1145dupAG [p.Ala383Glyfs(∗)8], c.1779dupT [p.Glu594(∗)], and c.2224_2225dupTT [p.Leu742Phefs(∗)7]) are predicted to truncate the protein, whereas the fourth (c.56C>T [p.Ala19Val]) is a missense variant of a conserved residue located at the cleavage site of the protein's signal peptide. All four affected individuals harboring a LRP6 mutation had a family history of tooth agenesis. LRP6 encodes a transmembrane cell-surface protein that functions as a co-receptor with members from the Frizzled protein family in the canonical Wnt/β-catenin signaling cascade. In this same pathway, WNT10A was recently identified as a major contributor in the etiology of non-syndromic oligodontia. We show that the LRP6 missense variant (c.56C>T) results in altered glycosylation and improper subcellular localization of the protein, resulting in abrogated activation of the Wnt pathway. Our results identify LRP6 variants as contributing to the etiology of non-syndromic autosomal-dominant oligodontia and suggest that this gene is a candidate for screening in DNA diagnostics.

Robin sequence (RS) can be defined as the combination of micrognathia and upper airway obstruction/glossoptosis causing neonatal respiratory problems, with or without a cleft palate and either isolated or non-isolated. Pathogenesis varies widely. We hypothesize that optimal treatment depends on pathogenesis and therefore patients should be stratified according to diagnosis. Here, we evaluate diagnoses and (presumed) pathogeneses in an RS cohort. Medical records of all RS patients presenting between 1995-2013 in three academic hospitals were evaluated. Four clinical geneticists re-evaluated all information, including initial diagnosis. Diagnoses were either confirmed, considered uncertain, or rejected. If uncertain or rejected, patients were re-evaluated. Subsequent results were re-discussed and a final conclusion was drawn. We included 191 RS patients. After re-evaluation and changing initial diagnoses in 48 of the 191 patients (25.1%), 37.7% of the cohort had isolated RS, 8.9% a chromosome anomaly, 29.3% a Mendelian disorder, and 24.1% no detectable cause. Twenty-two different Mendelian disorders were diagnosed, of which Stickler syndrome was most frequent. Stratification of diagnoses according to (presumed) pathogenic mechanism in 73 non-isolated patients with reliable diagnoses showed 43.9% to have a connective tissue dysplasia, 5.5% a neuromuscular disorder, 47.9% a multisystem disorder, and 2.7% an unknown mechanism. We diagnosed more non-isolated RS patients compared to other studies. Re-evaluation changed initial diagnosis in a quarter of patients. We suggest standardized re-evaluation of all RS patients. Despite the relatively high diagnostic yield pathogenesis could be determined in only 59.7% (71/119), due to limited insight in pathogenesis in diagnosed entities. Further studies into pathogenesis of entities causing RS are indicated.

We performed a clinical, biochemical, and genetic study in 16 patients from 11 families with adult-onset acid maltase deficiency. All patients were compound heterozygotes and carried the IVS1(-13T --> G) transversion on one allele; the second allele harbored either a deletion of a T at position 525 in exon 2 (7 probands, 64%) or a deletion of exon 18 (1 proband, 9%). Deterioration of handicap was related to age, and decrease in vital capacity to duration of the symptomatic stage. Respiratory insufficiency was never the first manifestation. The levels of activity of serum creatine kinase and of alpha-glucosidase in peripheral blood cells or muscle were helpful for the diagnosis, but did not have prognostic value. The adult form of acid maltase deficiency appears to be both clinically and genetically rather homogeneous; decrease of alpha-glucosidase activity is the final common pathway leading to destruction of muscle fibers and progression of muscle weakness over a period of years.

Blepharocheilodontic syndrome (BCDS) consists of lagophthalmia, ectropion of the lower eyelids, distichiasis, euryblepharon, cleft lip/palate and dental anomalies and has autosomal dominant inheritance with variable expression. We identified heterozygous variants in two genes of the cadherin-catenin complex, CDH1, encoding E-cadherin, and CTNND1, encoding p120 catenin delta1 in 15 of 17 BCDS index patients, as was recently described in a different publication. CDH1 plays an essential role in epithelial cell adherence; CTNND1 binds to CDH1 and controls the stability of the complex. Functional experiments in zebrafish and human cells showed that the CDH1 variants impair the cell adhesion function of the cadherin-catenin complex in a dominant-negative manner. Variants in CDH1 have been linked to familial hereditary diffuse gastric cancer and invasive lobular breast cancer; however, no cases of gastric or breast cancer have been reported in our BCDS cases. Functional experiments reported here indicated the BCDS variants comprise a distinct class of CDH1 variants. Altogether, we identified the genetic cause of BCDS enabling DNA diagnostics and counseling, in addition we describe a novel class of dominant negative CDH1 variants.