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The gene SURF1encodes a factor involved in the biogenesis of cytochrome coxidase, the last complex in the respiratory chain. Mutations of theSURF1gene result in Leigh syndrome and severe cytochromecoxidase deficiency. Analysis of seven unrelated patients with cytochrome coxidase deficiency and typical Leigh syndrome revealed different SURF1mutations in four of them. Only these four cases had associated demyelinating neuropathy. Three mutations were novel splicing-site mutations that lead to the excision of exon 6. Two different novel heterozygous mutations were found at the same guanine residue at the donor splice site of intron 6; one was a deletion, whereas the other was a transition [588+1G>A]. The third novel splicing-site mutation was a homozygous [516–2_516–1delAG] in intron 5. One patient only had a homozygous polymorphism in the middle of the intron 8 [835+25C>T]. Western blot analysis showed that Surf1 protein was absent in all four patients harboring mutations. Our studies confirm that theSURF1gene is an important nuclear gene involved in the cytochrome coxidase deficiency. We also show that Surf1 protein is not implicated in the assembly of other respiratory chain complexes or the pyruvate dehydrogenase complex.

The RCS rat presents an autosomal recessive retinal pigment epithelium dystrophy characterized by the outer segments of photoreceptors being phagocytosis-deficient. A systematic genetic study allowed us to restrict the interval containing the rdylocus to that between the markers D3Mit13 and D3Rat256. We report the chromosomal localization of the rat c-mergene in the cytogenetic bands 3q35-36, based on genetic analysis and radiation hybrid mapping. Using a systematic biocomputing analysis, we identified two strong related candidate genes encoding protein tyrosine kinase receptors of the AXLsubfamily. The comparison of their expression patterns in human and mice tissues suggested that the c-mergene was the best gene to screen for mutations. RCS rdy− and RCS rdy+ cDNAs were sequenced. The RCS rdy− cDNAs carried a significant deletion in the 5′ part of the coding sequence of the c-mergene resulting in a shortened aberrant transcript encoding a 20 amino acid peptide. The c-mergene contains characteristic motifs of neural cell adhesion. A ligand of the c-merreceptor, Gas6, exhibits antiapoptotic properties.

Based on the K8/JTS-1-mediated transfection technique, we developed an in vivo protocol for an efficient transfer of plasmid DNA to ocular cells. As determined with condensed plasmids containing reporter genes for either β-galactosidase (pcDNA-lacZ) or enhanced green fluorescent protein (pREP-EGFP), the immortalized human retinal epithelial cells RPE D407 and human embryonic kidney 293 cells can be transfected with typical efficiencies of 11 and 19%, respectively. Unlike 293 cells, RPE D407 cells had a reduced viability on transfection with both plasmids. In vivo, subretinal injections of DNA-K8/JTS-1 complexes revealed reporter gene expression in choroidal and RPE cells of normal pink-eyed Royal College of Surgeons (RCS) rats. The validity of this transfection technique in terms of retinal cell survival in RCS rats was then examined by using pREP-hFGF2 plasmid, which encodes the human basic fibroblast growth factor isoforms (hFGF2). Subretinal injection of pREP-hFGF2-K8/JTS-1 complexes into 3-week-old dystrophic RCS rat eyes reveals a delayed photoreceptor cell degeneration 60 days postinjection. In this case, the average analyzed field points with delayed cell dystrophy represent 14 to 17% of the retinal surface as compared with 2.6 and 4% in pREP5β and vehicle-injected eyes, respectively. Peptide-mediated in oculo transfection thus appears to be a promising technique for the treatment of retinal cell and photoreceptor degenerations.

Mutations in human BIGH3 (TGFB1), a gene identified after treatment of an adenocarcinoma cell line with TGF-β, have been observed in patients with granular Groenouw type I, Reis–Bu¨cklers, Thiel–Behnke, Avellino, and Lattice type I and IIIa, six autosomal dominant corneal dystrophies linked to chromosome 5q. In order to gain insight into the physiological role of this gene, we characterized the genomic structure of the mouse Bigh3 and its expression in murine embryos. The gene spans 30 kb on mouse chromosome 13 and has 17 exons. Embryonic expression of Bigh3 is observed in the mesenchyme of the first and second branchial archs as early as dpc 11.5 and is particularly strong in the mesenchyme of numerous tissues throughout all the development stages. In fetal eye, the expression is first seen at 11.5 dpc in the mesenchyme surrounding the optic stalk, extends toward the sclera and choroid by 14.3 dpc and reaches the cornea by 17.5 dpc. Because the physiological role of BIGH3/Bigh3 is still largely unknown, embryonic expression in organs like heart, vessels, and intestine may help to identify new functions which could be searched for in patients and in knock-out animal models. The characterization of the murine structure is a prerequisite for the making of such models.

We analyzed the distribution of FMR1, FXR1, FXR2 mRNA, and FMRP in whole normal human embryos and in the brains of normal and fragile X fetuses. The distributions of mRNA for the 3 genes in normal whole embryos and in the brains of normal male and female carrier fetuses were similar, with large amounts of mRNA in the nervous system and in several non-nervous system tissues. No FMR1 (mRNA and protein) was detected and no evident neuropathologic abnormalities found in the brains of male carrier fetuses, suggesting that the FMR1 product (FMRP) may have no crucial function in early stages of nervous system development. FXR1 and FXR2 mRNA had the same distribution and similar intensity in the brains of normal and pathologic fetuses (female and male carriers). The coexpression in the same tissues of FMR1, FXR1, and FXR2, associated with the normal expression of FXR1 and FXR2 and the absence of obvious neuropathological abnormalities in pathological brains, supports the notion that the FXR1 and FXR2 proteins partially compensate for FMRP function. However, the absence of significant overexpression of FXRI and FXR2 in pathological brains suggests that these genes do not compensate for the lack of FMR1 expression. Alternatively, FMR1, FXR1, and FXR2 proteins may not have compensatory functions, but instead may regulate functions by hetero or homo oligomerization, as suggested by other studies. Thus, a dominant negative effect of abnormal multimeric protein complexes lacking FMRP (e.g. by modification of FXR1 and FXR2 protein functions) may result in the fragile X syndrome phenotype.