Diabetic Embryopathy in C57BL/6J Mice

Altered Fetal Sex Ratio and Impact of the Splotch Allele

  1. Antonio F. Machado1,
  2. Ernest F. Zimmerman2,
  3. David N. Hovland Jr.3,
  4. Robert Weiss4 and
  5. Michael D. Collins1
  1. 1Department of Environmental Health Sciences, UCLA School of Public Health, Los Angeles, California
  2. 2Children’s Hospital Research Foundation and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio
  3. 3Allergan, Toxicology/Safety Evaluation, Irvine, California
  4. 4the Department of Biostatistics, UCLA School of Public Health, Los Angeles, California

    Abstract

    Maternal diabetes (types 1 and 2) induces a broad array of congenital malformations, including neural tube defects (NTDs), in humans. One of the difficulties associated with studying diabetic embryopathy is the rarity of individual malformations. In an attempt to develop a sensitive animal model for maternal diabetes–induced NTDs, the present study uses chemically induced diabetes in an inbred mouse model with or without the splotch (Sp) mutation, a putatively nonfunctional allele of Pax3. Pax3 deficiency has been associated with an increase in NTDs. Female C57BL/6J mice, either with or without the Sp allele, were injected intravenously with alloxan (100 mg/kg), and plasma glucose was measured 3 days later. A wide range of hyperglycemia was induced, and these diabetic mice were bred to C57BL/6J males, some carrying the Sp allele. Gestational-day-18 fetuses were examined for developmental malformations. Fetuses from matings in which either parent carried the Sp allele were genotyped by polymerase chain reaction. Maternal diabetes significantly decreased fetal weight and increased the number of resorptions and malformations, including NTDs. A significant correlation was found between the level of maternal hyperglycemia and the malformation rate. The sex ratio for live fetuses in diabetic litters was significantly skewed toward male fetuses. Matings involving the Sp allele yielded litters with significantly higher percentages of maternal diabetes–induced spina bifida aperta but not exencephaly, and this increase was shown to be associated with the presence of a single copy of the Sp allele in affected fetuses. Thus, Pax3 haploinsufficiency in this murine model of diabetic embryopathy is associated with caudal but not cranial NTDs.

    Footnotes

    • Address correspondence and reprint requests to Michael D. Collins, PhD, Department of Environmental Health Sciences, UCLA School of Public Health, 56-070 Center for the Health Sciences, Los Angeles, CA 90095-1772. E-mail: mdc{at}ucla.edu.

      Received for publication 8 November 1999 and accepted in revised form 25 January 2001.

      ALX, alloxan; PCR, polymerase chain reaction; NTD, neural tube defect; Sp, splotch; STZ, streptozotocin, UCLA, University of California–Los Angeles.

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