Identification of multiple sclerosis-associated genes

Resilient emotionality and molecular compensation in mice lacking the oligodendrocyte-specific gene Cnp1

Altered oligodendrocyte structure and function is implicated in major psychiatric illnesses, including low cell number and reduced oligodendrocyte-specific gene expression in major depressive disorder (MDD). These features are also observed in the unpredictable chronic mild stress (UCMS) rodent model of the illness, suggesting that they are consequential to environmental precipitants; however, whether oligodendrocyte changes contribute causally to low emotionality is unknown. Focusing on 2'-3'-cyclic nucleotide 3'-phosphodiesterase (Cnp1), a crucial component of axoglial communication dysregulated in the amygdala of MDD subjects and UCMS-exposed mice, we show that altered oligodendrocyte integrity can have an unexpected functional role in affect regulation. Mice lacking Cnp1 (knockout, KO) displayed decreased anxiety- and depressive-like symptoms (i.e., low emotionality) compared with wild-type animals, a phenotypic difference that increased with age (3-9 months). This phenotype was accompanied by increased motor activity, but was evident before neurodegenerative-associated motor coordination deficits (≤ 9-12 months). Notably, Cnp1(KO) mice were less vulnerable to developing a depressive-like syndrome after either UCMS or chronic corticosterone exposure. Cnp1(KO) mice also displayed reduced fear expression during extinction, despite normal amygdala c-Fos induction after acute stress, together implicating dysfunction of an amygdala-related neural network, and consistent with proposed mechanisms for stress resiliency. However, the Cnp1(KO) behavioral phenotype was also accompanied by massive upregulation of oligodendrocyte- and immune-related genes in the basolateral amygdala, suggesting an attempt at functional compensation. Together, we demonstrate that the lack of oligodendrocyte-specific Cnp1 leads to resilient emotionality. However, combined with substantial molecular changes and late-onset neurodegeneration, these results suggest the low Cnp1 seen in MDD may cause unsustainable and maladaptive molecular compensations contributing to the disease pathophysiology.

IgG allotypes and subclasses in Norwegian patients with multiple sclerosis

Multiple sclerosis (MS) is a multifactorial disease in which genetic and environmental factors apparently have a major influence on the susceptibility and course of the disease. In the present study we have investigated the genetic basis and subclass levels of IgG in MS. Hundred and thirty-six Norwegian patients with MS and 92 controls were genotyped for IgG allotypes of the GM and KM systems. IgG and IgG subclasses were quantified in sera from 115 MS patients and 20 controls. Neither GM nor KM allo-, haplo- or genotypes were significantly correlated with susceptibility, severity or course of the disease. The G1M (3) (3), G2M (23) (23) and G3M (5) (5) allotypes were significantly correlated with high serum levels of IgG3, whereas high IgG2 levels were correlated with G1M (3) (3) and G2M (23) (23) in both patients and controls. Serum levels of IgG subclasses were not significantly correlated with course or severity of the disease. The results indicate no major role for IgG allotypes or IgG subclass levels in the pathogenesis of MS.

Detecting low penetrance genes in cancer: the way ahead

The search for the genes responsible for many complex genetic diseases is well under way and has already been successful in some cases. The study of cancer as a complex genetic disease has lagged behind other conditions, largely because of particular problems that are associated with malignant disease. Cancer also, however, presents specific opportunities for gene identification, which are not found in many other diseases. While the methods of genetic mapping and gene cloning used for other complex diseases will be applied to cancer, these must almost certainly be complemented by other methods, such as the study of somatic mutations, cancer associated phenotypes, and modifier genes for Mendelian cancers. Here, we review the strategies available for identifying cancer predisposition genes of low and moderate penetrance.

Herpesviruses--a rationale for antiviral treatment in multiple sclerosis

In multiple sclerosis (MS), the extensive and long lasting search for viruses or other pathogens has hitherto failed to identify a common etiological agent. However, the beneficial effects by interferon-beta treatment in MS, although suggested to depend mainly on immunomodulation, might lend support to a viral involvement in the pathogenesis. The human herpesviruses have attracted interest since their recurrent modes of infection share some similarity with the relapsing-remitting course of MS, most members are readily detected within the brain, and several of these viruses may induce demyelination within the central nervous system in human hosts as well as in animal models. Accumulated diagnostic and epidemiological data are compatible with a role for the herpesviruses as possible cofactors rather than etiological agents, and recent studies showing early neuronal damage in MS patients focus attention on the neurotropic alpha-herpesviruses. Antiviral treatment trials with safe and effective drugs such as valaciclovir offer a possibility of testing the hypotheses concerning herpesviral involvement in MS.