Cerebral cavernous malformations (CCMs) are congenital vascular anomalies of the central nervous system that can result in hemorrhagic stroke, seizures, recurrent headaches, and focal neurologic deficits. Mutations in the gene KRIT1 are responsible for type 1 CCM (CCM1). We report that a novel gene, MGC4607, exhibits eight different mutations in nine families with type 2 CCM (CCM2). MGC4607, similar to the KRIT1 binding partner ICAP1alpha, encodes a protein with a phosphotyrosine-binding domain. This protein may be part of the complex pathway of integrin signaling that, when perturbed, causes abnormal vascular morphogenesis in the brain, leading to CCM formation.

Huntington's disease (HD) is a neurodegenerative disorder caused by the expansion of a polyglutamine stretch in the protein huntingtin (Htt). HD neurons are dysfunctional at multiple levels and have increased susceptibility to stress and apoptotic stimuli. We have discovered that synthesis of the ganglioside GM1 is reduced in fibroblasts from HD patients and in cell and animal models of HD, and that decreased GM1 levels contribute to heighten HD cell susceptibility to apoptosis. The apoptotic susceptibility is recapitulated through inhibition of ganglioside synthesis in wild-type striatal cells, suggesting that decreased GM1 levels might be one of the key events leading to HD pathogenesis and progression. Administration of GM1 restores ganglioside levels in HD cells and promotes activation of AKT and phosphorylation of mutant Htt, leading to decreased mutant Htt toxicity and increased survival of HD cells. Our data identify GM1 as a potential treatment for HD.

Huntington disease (HD) is a progressive neurodegenerative monogenic disorder caused by expansion of a polyglutamine stretch in the huntingtin (Htt) protein. Mutant huntingtin triggers neural dysfunction and death, mainly in the corpus striatum and cerebral cortex, resulting in pathognomonic motor symptoms, as well as cognitive and psychiatric decline. Currently, there is no effective treatment for HD. We report that intraventricular infusion of ganglioside GM1 induces phosphorylation of mutant huntingtin at specific serine amino acid residues that attenuate huntingtin toxicity, and restores normal motor function in already symptomatic HD mice. Thus, our studies have identified a potential therapy for HD that targets a posttranslational modification of mutant huntingtin with critical effects on disease pathogenesis.H untington disease (HD) is an inherited neurodegenerative monogenic disorder caused by the expansion of a polyglutamine stretch beyond 36 residues in the amino-terminal domain of huntingtin (Htt), a protein expressed in most tissues and cells. The mutation causes huntingtin to acquire toxic conformation/s and to affect neuronal function and viability. Medium-sized spiny neurons in the corpus striatum are most affected, but neurodegeneration also occurs in the cerebral cortex and, to a minor extent, in other brain areas, resulting in motor and psychiatric symptoms, as well as cognitive decline.The cellular and molecular mechanisms underlying HD pathogenesis are complex. Both loss and gain of function of mutant huntingtin contribute to cause a wide array of neuronal dysfunctions affecting cell signaling, gene transcription, axonal transport, cell and mitochondrial metabolism as well as neurotransmission (1).In recent years, a breakthrough in HD research has been the discovery that posttranslational modifications of mutant Htt are crucial modulators of mutant Htt toxicity (2-4). Phosphorylation at various serine residues prevents cleavage of mutant huntingtin into more toxic fragments, decreases neural cell death in vitro (5-10), and/or restores Htt functions that are compromised by the mutation (8, 11). The most dramatic effects have been described for huntingtin phosphorylation at serine 13 and serine 16. These two amino acid residues are part of the highly conserved amino-terminal "N17" domain of huntingtin, a domain that regulates huntingtin intracellular localization and association to cellular membranes (12, 13), as well as kinetics of mutant huntingtin aggregation (14,15). Phosphomimetic mutations of serine 13 and serine 16 by aspartic or glutamic acid substitution (S13D and S16D or S13E and S16E) decrease the toxicity of mutant huntingtin fragments in vitro (10, 16). In line with these studies, expression of a phosphomimetic (S13D and S16D) mutant form of expanded full-length huntingtin in a BACHD transgenic mouse model was shown to result in a normal phenotype, with no detectable signs of HD pathology by 12 mo (17).These findings suggest that pharmacological interventions that modulate cell sig...

Huntington disease is caused by a dominantly transmitted CAG repeat expansion mutation that is believed to confer a toxic gain of function on the mutant protein. Huntington disease patients with two mutant alleles are very rare. In other poly(CAG) diseases such as the dominant ataxias, inheritance of two mutant alleles causes a phenotype more severe than in heterozygotes. In this multicentre study, we sought differences in the disease features between eight homozygotes and 75 heterozygotes for the Huntington disease mutation. We identified subjects homozygous for the Huntington disease mutation by DNA testing and compared their clinical features (age at onset, symptom presentation, disease severity and disease progression) with those of a group of heterozygotes, who were assessed longitudinally. The age at onset of symptoms in the homozygote cases was within the range expected for heterozygotes with the same CAG repeat lengths, whereas homozygotes had a more severe clinical course. The observation of a more rapid decline in motor, cognitive and behavioural symptoms in homozygotes was consistent with the extent of neurodegeneration as available at imaging in three patients, and at the post-mortem neuropathological report in one case. Our analysis suggests that although homozygosity for the Huntington disease mutation does not lower the age at onset of symptoms, it affects the phenotype and the rate of disease progression. These data, once confirmed in a larger series of patients, point to the possibility that the mechanisms underlying age at onset and disease progression in Huntington disease may differ.

Huntington disease (HD) is a genetic neurodegenerative disorder for which there is currently no cure and no way to stop or even slow the brain changes it causes. In the present study, we aimed to investigate whether FTY720, the first approved oral therapy for multiple sclerosis, may be effective in HD models and eventually constitute an alternative therapeutic approach for the treatment of the disease. Here, we utilized preclinical target validation paradigms and examined the in vivo efficacy of chronic administration of FTY720 in R6/2 HD mouse model. Our findings indicate that FTY720 improved motor function, prolonged survival and reduced brain atrophy in R6/2 mice. The beneficial effect of FTY720 administration was associated with a significant strengthening of neuronal activity and connectivity and, with reduction of mutant huntingtin aggregates, and it was also paralleled by increased phosphorylation of mutant huntingtin at serine 13/16 residues that are predicted to attenuate protein toxicity.