Ocular retardation (or) is a murine eye mutation causing microphthalmia, a thin hypocellular retina and optic nerve aplasia. Here we show that mice carrying the OrJ allele have a premature stop codon in the homeobox of the Chx10 gene, a gene expressed at high levels in uncommitted retinal progenitor cells and mature bipolar cells. No CHX10 protein was detectable in the retinal neuroepithelium of orJ homozygotes. The loss of CHX10 leads both to reduced proliferation of retinal progenitors and to a specific absence of differentiated bipolar cells. Other major retinal cell types were present and correctly positioned in the mutant retina, although rod outer segments were short and retinal lamination was incomplete. These results indicate that Chx10 is an essential component in the network of genes required for the development of the mammalian eye, with profound effects on retinal progenitor proliferation and bipolar cell specification or differentiation. off

The generation of transgenic mice by pronuclear microinjection and their subsequent breeding has been more efficient with F1 or F2 zygotes than with zygotes of inbred strains because inbred mice generally have a relatively poor reproductive performance (1). However, an inbred genetic background is preferable for genetic analyses such as the transfer of one allele of a mouse gene into a strain carrying a different allele (2). Likewise, for insertional mutagenesis experiments, inbred strains eliminate ambiguity caused by different genetic backgrounds and segregating markers in the progeny. As reported here, the inbred strain FVB/N is a good breeder with large litters, and the fertilized eggs of this strain have large prominent pronuclei, which facilitate microinjection of DNA.The ancestor of FVB/N is an outbred colony of Swiss mice N:GP (NIH general purpose mouse) established at the National Institutes of Health in 1935. From the N:GP colony, a second colony N:NIH (NIH mouse) was established in the early 1940s. In 1966, a project was begun to develop two populations of N:NIH mice. Mice were inoculated with pertussis vaccines, followed by a challenge with histamine diphosphate. Two strains were selected for sensitivity and resistance and were designated as histamine sensitivity factor sensitive (HSFS/N) and histamine sensitivity factor resistant (HSFR/N), respectively. In the early 1970s, a group of mice at the eighth inbred generation from HSFS/N line were determined to carry the Fv-lb allele for sensitivity to the B strain of Friend leukemia virus, in contrast to N:NIH mice, which were sensitive to the N strain of this virus (Fv-J ") (F.L., unpublished results). These mice were then inbred and offspring were selected for Fv-Jb homozygosity. To avoid confusion with the HSFS/N strain that is Fv-1 ", the Fv-J b strain was designated as FVB for Friend virus B-type susceptibility. This strain has been maintained since the late 1970s as an inbred strain without selection for either pertussis vaccine sensitivity or virus type. In this report, we provide a detailed characterization of the genetic background of the FVB/N strain and the advantages of using the strain to generate and study transgenic mice.MATERIALS AND METHODS Mice. FVB/N mice (F38) were obtained from the National Institutes of Health Animal Genetic Resource.Pronudear Measurement. Embryos were obtained by in vitro fertilization of superovulated oocytes as described (3).Embryos developing pronuclei between 6 and 7 hr postinsemination were cultured an additional 5-6 hr and photographs were taken with Nomarski optics. Pronuclear volumes were calculated from their diameters measured along the equatorial planes perpendicular to the location of the polar bodies and excluding the zonae pellucidae. Only embryos exhibiting both pronuclei were used for analysis.Generation of Transgenic Mice. Pronuclear microinjections were performed by standard techniques (1). Mice were maintained on a cycle of light from 6:00 a.m. to 8:00 p.m.Superovulation was induced by administra...

Glaucomas are a major cause of blindness. Visual loss typically involves retinal ganglion cell death and optic nerve atrophy subsequent to a pathologic elevation of intraocular pressure (IOP). Some human glaucomas are associated with anterior segment abnormalities such as pigment dispersion syndrome (PDS) and iris atrophy with associated synechiae. The primary causes of these abnormalities are unknown, and their aetiology is poorly understood. We recently characterized a mouse strain (DBA/2J) that develops glaucoma subsequent to anterior segment changes including pigment dispersion and iris atrophy. Using crosses between mouse strains DBA/2J (D2) and C57BL/6J (B6), we now show there are two chromosomal regions that contribute to the anterior segment changes and glaucoma. Progeny homozygous for the D2 allele of one locus on chromosome 6 (called ipd) develop an iris pigment dispersion phenotype similar to human PDS. ipd resides on a region of mouse chromosome 6 with conserved synteny to a region of human chromosome 7q that is associated with human PDS. Progeny homozygous for the D2 allele of a different locus on chromosome 4 (called isa) develop an iris stromal atrophy phenotype (ISA). The Tyrpl gene is a candidate for isa and likely causes ISA via a mechanism involving pigment production. Progeny homozygous for the D2 alleles of both ipd and isa develop an earlier onset and more severe disease involving pigment dispersion and iris stromal atrophy.

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