Substitutive cell therapy using fetal striatal grafts has demonstrated preliminary clinical success in patients with Huntington's disease, but the logistics required for accessing fetal cells preclude its extension to the relevant population of patients. Human embryonic stem (hES) cells theoretically meet this challenge, because they can be expanded indefinitely and differentiated into any cell type. We have designed an in vitro protocol combining substrates, media, and cytokines to push hES cells along the neural lineage, up to postmitotic neurons expressing striatal markers. The therapeutic potential of such hES-derived cells was further substantiated by their in vivo differentiation into striatal neurons following xenotransplantation into adult rats. Our results open the way toward hES cell therapy for Huntington's disease. Long-term proliferation of human neural progenitors leads, however, to xenograft overgrowth in the rat brain, suggesting that the path to the clinic requires a way to switch them off after grafting.cell therapy ͉ Huntington's disease ͉ striatum ͉ cell differentiation ͉ overgrowth

Alterations of mitochondrial function may play a central role in neuronal death in Huntington's disease (HD). However, the molecular mechanisms underlying such functional deficits of mitochondria are not elucidated yet. We herein showed that the expression of two important constituents of mitochondrial complex II, the 30-kDa iron-sulfur (Ip) subunit and the 70-kDa FAD (Fp) subunit, was preferentially decreased in the striatum of HD patients compared with controls. We also examined several mitochondrial proteins in striatal neurons that were infected with lentiviral vectors coding for the N-terminus part of huntingtin (Htt) with either a pathological (Htt171-82Q) or physiological (Htt171-19Q) polyglutamine tract. Compared with Htt171-19Q, expression of Htt171-82Q preferentially decreased the levels of Ip and Fp subunits and affected the dehydrogenase activity of the complex. The Htt171-82Q-induced preferential loss of complex II was not associated with a decrease in mRNA levels, suggesting the involvement of a posttranscriptional mechanism. Importantly, the overexpression of either Ip or Fp subunit restored complex II levels and blocked mitochondrial dysfunction and striatal cell death induced by Htt171-82Q in striatal neurons. The present results strongly suggest that complex II defects in HD may be instrumental in striatal cell death. INTRODUCTIONHuntington's disease (HD) is a progressive neurodegenerative disorder caused by an abnormal expansion of a CAG repeat located in exon 1 of the gene encoding for the Huntingtin protein (Htt; The Huntington's Disease Collaborative Research Group, 1993). The mutation induces at least in part a loss of function, since wild-type Htt plays an important role in cell survival (Zuccato et al., 2003). In addition, the CAG repeat expansion leads to an abnormal polyglutamine (polyQ) tract that confers a new toxic function to full-length mutated Htt and/or short N-terminus fragments of the protein (Wellington et al., 2002;Li and Li, 2004). However, the mechanisms underlying the neuronal death induced by the polyQ expansion remain elusive.One hypothesis is that mitochondrial dysfunction is involved in striatal cell death in HD. HD patients display early striatal hypometabolism (for review, Beal, 1992), increase in lactate brain concentrations (Koroshetz et al., 1997;Jenkins et al., 1998), and reduced production of ATP in muscles (Lodi et al., 2000). Mitochondria isolated from cell expressing mutated Htt show decreased membrane potential, a defect in Ca 2ϩ homeostasis, and higher susceptibility to Ca 2ϩ -induced permeability transition (Panov et al., 2002;Choo et al., 2004).The mitochondrial hypothesis is also supported by the observation that systemic administration of the complex II inhibitor 3-nitropropionic acid (3NP) produces in rats and in nonhuman primates preferential degeneration of the striatum, abnormal movements, and frontal type cognitive deficits that are highly reminiscent of HD (for review Brouillet et al., 1999). In addition, complex II activity is severely impaired ...

By analyzing five human embryonic stem (hES) cell lines over long-term culture, we identified a recurrent genomic instability in the human genome. An amplification of 2.5-4.6 Mb at 20q11.21, encompassing approximately 23 genes in common, was detected in four cell lines of different origins. This amplification, which has been associated with oncogenic transformation, may provide a selective advantage to hES cells in culture.

Introduction: Primary open-angle glaucoma (POAG) is a leading cause of visual impairment worldwide and a complex genetic disorder that affects mostly adults. Mutations in the MYOCILIN (MYOC) and OPTINEURIN genes account for rare forms with a Mendelian inheritance and for ,5% of all POAG cases. The CYP1B1 gene, a member of the cytochrome P450 gene family, is a major cause of primary congenital glaucoma (PCG), a rare and severely blinding disease with recessive inheritance. However, CYP1B1 mutations have also been associated with cases of juvenile-onset glaucoma in some PCG families or shown to modify the age of onset of glaucoma linked to a MYOC mutation in a large family. Objective: To investigate the role of CYP1B1 mutations in POAG predisposition, irrespective of the presence of a MYOC mutation. Methods and subjects: CYP1B1 coding region variation was characterised by denaturing high performance liquid chromatography (DHPLC) and sequencing in 236 unrelated French Caucasian POAG patients and 47 population-matched controls. Results: Eleven (4.6%) patients carried one or two mutated CYP1B1 gene(s) and no MYOC mutation. They showed juvenile or middle-age onset of disease (median age at diagnosis, 40 years, range 13-52), significantly earlier than in non-carrier patients. Apart from one, all mutations detected in POAG patients were previously associated with PCG. Conclusion: CYP1B1 mutations might pose a significant risk for early-onset POAG and might also modify glaucoma phenotype in patients who do not carry a MYOC mutation.