Embryonic defence mechanisms against glucose-dependent oxidative stress require enhanced expression of Alx3 to prevent malformations during diabetic pregnancy

Patricia García-Sanz,Rosario Moratalla,Mercedes Mirasierra,Mario Vallejo

doi:10.1038/s41598-017-00334-1

Abstract

Oxidative stress constitutes a major cause for increased risk of congenital malformations associated to severe hyperglycaemia during pregnancy. Mutations in the gene encoding the transcription factor ALX3 cause congenital craniofacial and neural tube defects. Since oxidative stress and lack of ALX3 favour excessive embryonic apoptosis, we investigated whether ALX3-deficiency further increases the risk of embryonic damage during gestational hyperglycaemia in mice. We found that congenital malformations associated to ALX3-deficiency are enhanced in diabetic pregnancies. Increased expression of genes encoding oxidative stress-scavenging enzymes in embryos from diabetic mothers was blunted in the absence of ALX3, leading to increased oxidative stress. Levels of ALX3 increased in response to glucose, but ALX3 did not activate oxidative stress defence genes directly. Instead, ALX3 stimulated the transcription of Foxo1, a master regulator of oxidative stress-scavenging genes, by binding to a newly identified binding site located in the Foxo1 promoter. Our data identify ALX3 as an important component of the defence mechanisms against the occurrence of developmental malformations during diabetic gestations, stimulating the expression of oxidative stress-scavenging genes in a glucose-dependent manner via Foxo1 activation. Thus, ALX3 deficiency provides a novel molecular mechanism for developmental defects arising from maternal hyperglycaemia.

Highlights

Maternal pre-gestational diabetes is a major cause for increased risk of embryonic damage and congenital malformations during pregnancy[1, 2]
In line with our previous findings[35], fasting blood glucose levels were higher in non-pregnant Alx3-deficient than in wild type females, but they remained with normal range (
All these data indicate that Alx3-deficient non-pregnant females have mild glucose intolerance, but this is not aggravated during pregnancy, being similar to the glucose intolerance associated with pregnancy in wild type animals

Summary

Introduction

Maternal pre-gestational diabetes is a major cause for increased risk of embryonic damage and congenital malformations during pregnancy[1, 2]. The gene encoding the homeodomain transcription factor ALX3 is expressed in mesenchymal cells in mouse mid gestation embryos and regulates important developmental processes[30,31,32,33] Recessive mutations in this gene in humans or its deficiency in mice result in craniofacial malformations as well as in cranial neural tube defects accompanied by increased apoptosis in the forehead mesenchyme[32, 34]. In mice, this phenotype exhibits a characteristic incomplete penetrance so that a considerable proportion of Alx3-deficient embryos are apparently normal and viable[32, 33]. Based on these observations and on the association between Alx3-deficiency and apoptosis[32, 35], we investigated whether Alx3-deficient embryos are more vulnerable to the harmful effects of hyperglycaemia during diabetic pregnancy

Methods

Results

Conclusion