A murine model of hereditary hemorrhagic telangiectasia
Annie Bourdeau, Daniel J. Dumont, Michelle Letarte
Annie Bourdeau, Daniel J. Dumont, Michelle Letarte
View: Text | PDF
Article

A murine model of hereditary hemorrhagic telangiectasia

Abstract

Endoglin (CD105), an accessory protein of the TGF-β receptor superfamily, is highly expressed on endothelial cells. Hereditary hemorrhagic telangiectasia type 1 (HHT1) is associated with mutations in the Endoglin gene, leading to haploinsufficiency. To generate a disease model and ascertain the role of endoglin in development, we generated mice lacking 1 or both copies of the gene. Endoglin null embryos die at gestational day 10.0–10.5 due to defects in vessel and heart development. Vessel formation appears normal until hemorrhage occurs in yolk sacs and embryos. The primitive vascular plexus of the yolk sac fails to mature into defined vessels, and vascular channels dilate and rupture. Internal bleeding is seen in the peritoneal cavity, implying fragile vessels. Heart development is arrested at day 9.0, and the atrioventricular canal endocardium fails to undergo mesenchymal transformation and cushion-tissue formation. These data suggest that endoglin is critical for both angiogenesis and heart valve formation. Some heterozygotes, either with an inbred 129/Ola or mixed C57BL/6-129/Ola background, show signs of HHT, such as telangiectases or recurrent nosebleeds. In this murine model of HHT, it appears that epigenetic factors and modifier genes, some of which are present in 129/Ola, contribute to disease heterogeneity.

Authors

Annie Bourdeau, Daniel J. Dumont, Michelle Letarte

×

Figure 1

Options: View larger image (or click on image) Download as PowerPoint
Generation of End–/– mice. (a) Targeting strategy. Homologous recombinat...
Generation of End–/– mice. (a) Targeting strategy. Homologous recombination deletes 609 bp of the End gene including exon 1 (E1; 66 bp), placing the LacZ gene under control of its promoter. The targeting construct contains a 1.4-kb SmaI fragment (5′ HR) and a 5.1-kb SmaI-BglII fragment (3′ HR) of the End gene flanking the LacZ-Neo cassette. Proper recombination events were screened by Southern blot analysis with 5′ external and LacZ internal probes. Bm, BamHI; Bg, BglII; EI, EcoRI; Sa, SacI; Sc, ScaI; Sm, SmaI; Xb, XbaI. (b) Identification of targeted ES cell lines. DNA from 2 geneticin- and ganciclovir-resistant targeted ES cells (4A-11, 4A-36) and a wild-type clone (WT) were digested with ScaI. The 5.4-kb WT and 7.3-kb recombinant alleles hybridizing with the 5′ external probe and the recombinant allele reacting with the LacZ probe are shown. (c) Genotyping of embryos by multiplex PCR. DNA from yolk sacs of an E9.5 litter derived from a C57BL/6 End+/– mating is shown; #21 represents the mother and C represents the PCR control reaction without DNA. Primers ME1F and ME1R amplify normal exon 1 (300 bp), ME2F and ME2R amplify normal exon 2 (383 bp), and ME1F and MEZR specifically amplify the recombinant product (476 bp). (d) Absence of endoglin mRNA in End–/– embryos. RNA was prepared from the same embryos as in c and analyzed for endoglin and β-actin mRNA by RT-PCR.