CDH1 Mutation Distribution and Type Suggests Genetic Differences between the Etiology of Orofacial Clefting and Gastric Cancer

E-cadherin variants associated with oral facial clefts trigger aberrant cell motility in a REG1A-dependent manner

BACKGROUND

Germline mutations of E-cadherin contribute to hereditary diffuse gastric cancer (HDGC) and congenital malformations, such as oral facial clefts (OFC). However, the molecular mechanisms through which E-cadherin loss-of-function triggers distinct clinical outcomes remain unknown. We postulate that E-cadherin-mediated disorders result from abnormal interactions with the extracellular matrix and consequent aberrant intracellular signalling, affecting the coordination of cell migration.

METHODS

Herein, we developed in vivo and in vitro models of E-cadherin mutants associated with either OFC or HDGC. Using a Drosophila approach, we addressed the impact of the different variants in cell morphology and migration ability. By combining gap closure migration assays and time-lapse microscopy, we further investigated the migration pattern of cells expressing OFC or HDGC variants. The adhesion profile of the variants was evaluated using high-throughput ECM arrays, whereas RNA sequencing technology was explored for identification of genes involved in aberrant cell motility.

RESULTS

We have demonstrated that cells expressing OFC variants exhibit an excessive motility performance and irregular leading edges, which prevent the coordinated movement of the epithelial monolayer. Importantly, we found that OFC variants promote cell adhesion to a wider variety of extracellular matrices than HDGC variants, suggesting higher plasticity in response to different microenvironments. We unveiled a distinct transcriptomic profile in the OFC setting and pinpointed REG1A as a putative regulator of this outcome. Consistent with this, specific RNAi-mediated inhibition of REG1A shifted the migration pattern of OFC expressing cells, leading to slower wound closure with coordinated leading edges.

CONCLUSIONS

We provide evidence that E-cadherin variants associated with OFC activate aberrant signalling pathways that support dynamic rearrangements of cells towards improved adaptability to the microenvironment. This proficiency results in abnormal tissue shaping and movement, possibly underlying the development of orofacial malformations.

Simultaneous Occurrence of Hypospadias and Bilateral Cleft Lip and Jaw in a Crossbred Calf: Clinical, Computer Tomographic, and Genomic Characterization

Congenital abnormalities in animals, including abnormalities of the cleft lip and jaw and hypospadias have been reported in all domesticated species. They are a major concern for breeders due to the increased economic loss they entail. In this article, we described a congenital bilateral cheilognathoschisis (cleft lip and jaw) with campylognathia in association with penile hypospadias and preputial hypoplasia with failure of preputial fusion in a Bos taurus crossbred Piedmontese × Wagyu calf. Clinical examination, computed tomography, and whole genome sequencing were performed to describe and identify a possible cause of the abnormalities. Clinical examination revealed a bilateral cheilognathoschisis of approximately 4 cm in length and 3 cm in width in the widest part, with computer tomography analyses confirming the bilateral absence of the processus nasalis of the incisive bone and the lateral deviation of the processus palatinus towards the left side. Genomic data analyses identified 13 mutations with a high impact on the products of the following overlapped genes: ACVR1, ADGRA2, BHMT2, BMPR1B, CCDC8, CDH1, EGF, F13A1, GSTP1, IRF6, MMP14, MYBPHL, and PHC2 with ADGRA2, EGF, F13A1, GSTP1, and IRF6 having mutations in a homozygous state. The whole genome investigation indicates the involvement of multiple genes in the birth defects observed in this case.

Multiancestry genomic and transcriptomic analysis of gastric cancer

Gastric cancer is among the most common malignancies worldwide, characterized by geographical, epidemiological and histological heterogeneity. Here, we report an extensive, multiancestral landscape of driver events in gastric cancer, involving 1,335 cases. Seventy-seven significantly mutated genes (SMGs) were identified, including ARHGAP5 and TRIM49C. We also identified subtype-specific drivers, including PIGR and SOX9, which were enriched in the diffuse subtype of the disease. SMGs also varied according to Epstein-Barr virus infection status and ancestry. Non-protein-truncating CDH1 mutations, which are characterized by in-frame splicing alterations, targeted localized extracellular domains and uniquely occurred in sporadic diffuse-type cases. In patients with gastric cancer with East Asian ancestry, our data suggested a link between alcohol consumption or metabolism and the development of RHOA mutations. Moreover, mutations with potential roles in immune evasion were identified. Overall, these data provide comprehensive insights into the molecular landscape of gastric cancer across various subtypes and ancestries.

Frequent cleft lip and palate in families with pathogenic germline CDH1 variants

Pathogenic and likely pathogenic (P/LP) germline variants in the tumor suppressor gene CDH1 (E-cadherin) result in increased lifetime risk of diffuse-type gastric cancer and lobular breast cancer. CDH1 variants are also associated with hereditary cleft lip and palate (CLP), the mechanism of which is not well understood. We sought to determine the prevalence of CLP in families who carry P/LP CDH1 variants. Patients with P/LP CDH1 variants who were enrolled in a prospective clinical trial were reviewed (NCT03030404). The cohort included 299 individuals from 153 families that had 80 unique P/LP variants in CDH1. The rate of CLP was 19% (29/153) in families reporting CLP in at least one family member, and 2.7% (8/299) among individuals with confirmed germline CDH1 P/LP variants. There were 22 unique variants in CDH1 among the 29 families that reported CLP, or a CLP rate of 27.5% per variant (22/80). 10 of the variants were not previously reported to be associated with CLP. We observed that 24% (7/29) of CLP-associated gene variants involved large-scale (≥1 exon) deletions. Among families with CLP, 69% (20/29) had a member diagnosed with gastric cancer, and 79% (23/29) had a member with breast cancer, which were similar to rates observed in non-CLP families (p >0.3 for both). Our analysis suggests that the prevalence of CLP in families with germline CDH1 P/LP variants was high in this large cohort, and there was no genotype-phenotype pattern. Genetic testing for CDH1 variants should be considered in families with CLP and history of either diffuse-type gastric or lobular breast cancer.

Mouse models in palate development and orofacial cleft research: Understanding the crucial role and regulation of epithelial integrity in facial and palate morphogenesis

Cleft lip and cleft palate are common birth defects resulting from genetic and/or environmental perturbations of facial development in utero. Facial morphogenesis commences during early embryogenesis, with cranial neural crest cells interacting with the surface ectoderm to form initially partly separate facial primordia consisting of the medial and lateral nasal prominences, and paired maxillary and mandibular processes. As these facial primordia grow around the primitive oral cavity and merge toward the ventral midline, the surface ectoderm undergoes a critical differentiation step to form an outer layer of flattened and tightly connected periderm cells with a non-stick apical surface that prevents epithelial adhesion. Formation of the upper lip and palate requires spatiotemporally regulated inter-epithelial adhesions and subsequent dissolution of the intervening epithelial seam between the maxillary and medial/lateral nasal processes and between the palatal shelves. Proper regulation of epithelial integrity plays a paramount role during human facial development, as mutations in genes encoding epithelial adhesion molecules and their regulators have been associated with syndromic and non-syndromic orofacial clefts. In this chapter, we summarize mouse genetic studies that have been instrumental in unraveling the mechanisms regulating epithelial integrity and periderm differentiation during facial and palate development. Since proper epithelial integrity also plays crucial roles in wound healing and cancer, understanding the mechanisms regulating epithelial integrity during facial development have direct implications for improvement in clinical care of craniofacial patients.

To Stick or Not to Stick: Adhesions in Orofacial Clefts

Morphogenesis requires a tight coordination between mechanical forces and biochemical signals to inform individual cellular behavior. For these developmental processes to happen correctly the organism requires precise spatial and temporal coordination of the adhesion, migration, growth, differentiation, and apoptosis of cells originating from the three key embryonic layers, namely the ectoderm, mesoderm, and endoderm. The cytoskeleton and its remodeling are essential to organize and amplify many of the signaling pathways required for proper morphogenesis. In particular, the interaction of the cell junctions with the cytoskeleton functions to amplify the behavior of individual cells into collective events that are critical for development. In this review we summarize the key morphogenic events that occur during the formation of the face and the palate, as well as the protein complexes required for cell-to-cell adhesions. We then integrate the current knowledge into a comprehensive review of how mutations in cell-to-cell adhesion genes lead to abnormal craniofacial development, with a particular focus on cleft lip with or without cleft palate.

Gastric cancer genetic predisposition and clinical presentations: Established heritable causes and potential candidate genes

Tumour risk syndromes (TRS) are characterized by an increased risk of early-onset cancers in a familial context. High cancer risk is mostly driven by loss-of-function variants in a single cancer-associated gene. Presently, predisposition to diffuse gastric cancer (DGC) is explained by CDH1 and CTNNA1 pathogenic and likely pathogenic variants (P/LP), causing Hereditary Diffuse Gastric Cancer (HDGC); while APC promoter 1B single nucleotide variants predispose to Gastric Adenocarcinoma and Proximal Polyposis of the Stomach (GAPPS). Familial Intestinal Gastric Cancer (FIGC), recognized as a GC-predisposing disease, remains understudied and genetically unsolved. GC can also occur in the spectrum of other TRS. Identification of heritable causes allows defining diagnostic testing criteria, helps to clinically classify GC families into the appropriate TRS, and allows performing pre-symptomatic testing identifying at-risk individuals for downstream surveillance, risk reduction and/or treatment. However, most of HDGC, some GAPPS, and most FIGC patients/families remain unsolved, expecting a heritable factor to be discovered. The missing heritability in GC-associated tumour risk syndromes (GC-TRS) is likely explained not by a single major gene, but by a diversity of genes, some, predisposing to other TRS. This would gain support if GC-enriched small families or apparently isolated early-onset GC cases were hiding a family history compatible with another TRS. Herein, we revisited current knowledge on GC-TRS, and searched in the literature for individuals/families bearing P/LP variants predisposing for other TRS, but whose probands display a clinical presentation and/or family history also fitting GC-TRS criteria. We found 27 families with family history compatible with HDGC or FIGC, harbouring 28 P/LP variants in 16 TRS-associated genes, mainly associated with DNA repair. PALB2 or BRCA2 were the most frequently mutated candidate genes in individuals with family history compatible with HDGC and FIGC, respectively. Consolidation of PALB2 and BRCA2 as HDGC- or FIGC-associated genes, respectively, holds promise and worth additional research. This analysis further highlighted the influence, that proband's choice and small or unreported family history have, for a correct TRS diagnosis, genetic screening, and disease management. In this review, we provide a rational for identification of particularly relevant candidate genes in GC-TRS.