The effect of maternal diabetes on the Wnt/PCP pathway during embryogenesis as reflected in the developing mouse eye

Abstract

Embryopathies that develop as a consequence of maternal diabetes have been studied intensely in both experimental and clinical scenarios. Accordingly, hyperglycaemia has been shown to downregulate the expression of elements in the non-canonical Wnt-PCP pathway, such as the Dishevelled-associated activator of morphogenesis 1 (Daam1) and Vangl2. Daam1 is a formin that is essential for actin polymerization and for cytoskeletal reorganization, and it is expressed strongly in certain organs during mouse development, including the eye, neural tube and heart. Daam1gt/gt and Daam1gt/+ embryos develop ocular defects (anophthalmia or microphthalmia) that are similar to those detected as a result of hyperglycaemia. Indeed, studying the effects of maternal diabetes on the Wnt-PCP pathway demonstrated that there was strong association with the Daam1 genotype, whereby the embryopathy observed in Daam1gt/+ mutant embryos of diabetic dams was more severe. There was evidence that embryonic exposure to glucose in vitro diminishes the expression of genes in the Wnt-PCP pathway, leading to altered cytoskeletal organization, cell shape and cell polarity in the optic vesicle. Hence, the Wnt-PCP pathway appears to influence cell morphology and cell polarity, events that drive the cellular movements required for optic vesicle formation and that, in turn, are required to maintain the fate determination. Here, we demonstrate that the Wnt-PCP pathway is involved in the early stages of mouse eye development and that it is altered by diabetes, provoking the ocular phenotype observed in the affected embryos.

The interaction of maternal diabetes with mutations that affect folate metabolism and how they affect the development of neural tube defects in mice

“…The three genotypes had a clear impact on the final phenotype (for both Mthfr and Folr1 ), demonstrating the potential risk of maternal diabetes and any other environmental factor that alters gene expression, relevant to embryonic development. Indeed, maternal diabetes appears to be capable of making an embryonic recessive mutation behave like a dominant mutation, or of increasing the incidence of a rare phenotype, as observed previously . Here, the incidence of embryos with NTDs increased with the reduction in embryonic Mthfr dosage and therefore activity (see, in a maternal hyperglycemic background.…”

“…As such, we exposed embryos to hyperhomocysteinemic conditions to recapitulate the homocysteine accumulation that can occur during folate deficiency. Embryos were divided into four equivalent groups depending on the treatment received, and after 18 hours in culture, the embryos were evaluated for gross external malformations: controls (n = 42), embryos exposed to PBS alone; homocysteine embryos (n = 30) exposed to 0.5 mM homocysteine (based on Reference ; glucose embryos (n = 39), exposed to 20 mM glucose (based on Reference ; and glucose and homocysteine embryos (n = 46), exposed to 20 mM glucose and 0.5 mM homocysteine (data summarized in Table ). Those embryos with less than 16 somites before culture that reached >19 somites after culture were evaluated for cranial closure.…”

“…Diabetes‐induced morphogenetic defects have been associated with changes in gene expression, and several have been linked to embryopathies (like Pax3 ) or genes involved in Wnt signaling . Alterations to the Wnt‐PCP pathway disrupt the distribution of apical actin microfilaments in the caudal and cranial neural plate, and this disrupts the polarization and morphology of the cells in this region, delaying NT closure and possibly driving NTDs .…”

“…Maternal diabetes is also a well‐known environmental risk factor for congenital malformations, producing potentially adverse effects by altering the expression of genes involved in the signaling and metabolic pathways implicated in embryogenesis. These include genes in the Wnt‐planar cell polarity pathway (Wnt‐PCP) and those involved in folate metabolism, oxidative stress, apoptosis, or proliferation . As such, maternal hyperglycemia can adversely affect major signaling events and, if an embryo also carries a mutation in a gene involved in such an event, the resulting phenotype would be expected to be more severe.…”

Epigenetic mechanisms underlying maternal diabetes-associated risk of congenital heart disease

“…For example, peaks associated with the genes in the BMP, FoxP1, and Wnt cardiac morphogenetic signaling pathways were identified, and they have been linked to increased risk of fetal neurologic and cardiac developmental defects in matDM-exposed embryos (61)(62)(63)(64)(65). HG stress resulted in dysregulation of chromatin accessibility of genes important for reorganizing actin cytoskeleton, cell polarity, and alignment during tissue morphogenesis (66,67). Interestingly, our data demonstrated that peaks associated with genes involved in chromatin regulation were also altered in the setting of HG (Supplemental Figure 8, A-C, and Supplemental Table 17).…”