In vivo validation of late-onset Alzheimer's disease genetic risk factors

INTRODUCTION

Genome-wide association studies have identified over 70 genetic loci associated with late-onset Alzheimer's disease (LOAD), but few candidate polymorphisms have been functionally assessed for disease relevance and mechanism of action.

METHODS

Candidate genetic risk variants were informatically prioritized and individually engineered into a LOAD-sensitized mouse model that carries the AD risk variants APOE ε4/ε4 and Trem2*R47H. The potential disease relevance of each model was assessed by comparing brain transcriptomes measured with the Nanostring Mouse AD Panel at 4 and 12 months of age with human study cohorts.

RESULTS

We created new models for 11 coding and loss-of-function risk variants. Transcriptomic effects from multiple genetic variants recapitulated a variety of human gene expression patterns observed in LOAD study cohorts. Specific models matched to emerging molecular LOAD subtypes.

DISCUSSION

These results provide an initial functionalization of 11 candidate risk variants and identify potential preclinical models for testing targeted therapeutics.

HIGHLIGHTS

A novel approach to validate genetic risk factors for late-onset AD (LOAD) is presented. LOAD risk variants were knocked in to conserved mouse loci. Variant effects were assayed by transcriptional analysis. Risk variants in Abca7, Mthfr, Plcg2, and Sorl1 loci modeled molecular signatures of clinical disease. This approach should generate more translationally relevant animal models.

In vivo validation of late-onset Alzheimer's disease genetic risk factors

Introduction

Genome-wide association studies have identified over 70 genetic loci associated with late-onset Alzheimer's disease (LOAD), but few candidate polymorphisms have been functionally assessed for disease relevance and mechanism of action.

Methods

Candidate genetic risk variants were informatically prioritized and individually engineered into a LOAD-sensitized mouse model that carries the AD risk variants APOE4 and Trem2*R47H. Potential disease relevance of each model was assessed by comparing brain transcriptomes measured with the Nanostring Mouse AD Panel at 4 and 12 months of age with human study cohorts.

Results

We created new models for 11 coding and loss-of-function risk variants. Transcriptomic effects from multiple genetic variants recapitulated a variety of human gene expression patterns observed in LOAD study cohorts. Specific models matched to emerging molecular LOAD subtypes.

Discussion

These results provide an initial functionalization of 11 candidate risk variants and identify potential preclinical models for testing targeted therapeutics.

Multipotent stem cells from the mouse basal forebrain contribute GABAergic neurons and oligodendrocytes to the cerebral cortex during embryogenesis

During CNS development, cell migrations play an important role, adding to the cellular complexity of different regions. Earlier studies have shown a robust migration of cells from basal forebrain into the overlying dorsal forebrain during the embryonic period. These immigrant cells include GABAergic neurons that populate the cerebral cortex and hippocampus. In this study we have examined the fate of other basal forebrain cells that migrate into the dorsal forebrain, identifying basal cells using an antibody that recognizes both early (dlx1/2) and late (dlx 5/6) members of the dlx homeobox gene family. We found that a subpopulation of cortical and hippocampal oligodendrocytes are also ventral-derived. We traced the origin of these cells to basal multipotent stem cells capable of generating both GABAergic neurons and oligodendrocytes. A clonal analysis showed that basal forebrain stem cells produce significantly more GABAergic neurons than dorsal forebrain stem cells from the same embryonic age. Moreover, stem cell clones from basal forebrain are significantly more likely to contain both GABAergic neurons and oligodendrocytes than those from dorsal. This indicates that forebrain stem cells are regionally specified. Whereas dlx expression was not detected within basal stem cells growing in culture, these cells produced dlx-positive products that are capable of migration. These data indicate that the developing cerebral cortex incorporates both neuronal and glial products of basal forebrain and suggest that these immigrant cells arise from a common progenitor, a dlx-negative basal forebrain stem cell.

Pregnancy outcome in patients with repeat visits to the labor observation area near term

Patients whose pregnancies are near term and who repeatedly visit the labor observation area but are found not to be in labor and have no clear diagnosis for their complaints remain a source of concern for the obstetrician. In order to determine whether this is a population with special perinatal risks, such cases were reviewed over a 4-month period at Charity Hospital in New Orleans. Seventy-one patients were identified who had repeatedly visited the labor observation area near term. Compared with those in the general obstetrics population, these patients had a significantly increased risk of cesarean section for "failure to progress." Repeat visitors to the labor observation area should be viewed as having a high risk for later abnormalities of active labor. Careful management of labor abnormalities in such patients could theoretically lower their need for cesarean section.