Robust dysregulation of gene expression in substantia nigra and striatum in Parkinson's disease.

Large-scale genomics approaches are now widely utilized to study a myriad of human diseases. These powerful techniques, when combined with data analysis tools, detect changes in transcript abundance in diseased tissue relative to control. We hypothesize that specific differential gene expression underlies important pathogenic processes in Parkinson's disease, which is characterized by the gradual loss of dopaminergic neurons in the substantia nigra and consequent loss of dopamine in the striatum. We have therefore examined gene expression levels in the human parkinsonian nigrostriatal pathway, and compared them with those of neurologically normal controls. Using unsupervised clustering methods, we demonstrate that relatively few genes' expression levels can effectively distinguish between disease and control brains. Further, we identify several interesting patterns of gene expression that illuminate pathogenic cascades in Parkinson's disease. In particular is the robust loss of synaptic gene expression in diseased substantia nigra and striatum.

Temporal evolution of mouse striatal gene expression following MPTP injury.

The gradual loss of striatal dopamine and dopaminergic neurons residing in the substantia nigra (SN) causes parkinsonism characterized by slow, halting movements, rigidity, and resting tremor when neuronal loss exceeds a threshold of approximately 80%. It is estimated that there is extensive compensation for several years prior to symptom onset, during which vulnerable neurons asynchronously die. Recent evidence would argue that much of the compensatory response of the nigrostriatal system is multimodal including both pre-synaptic and striatal mechanisms. Although parkinsonism may have multiple causes, the classic syndrome, Parkinson's disease (PD), is frequently modeled in small animals by repeated administration of the selective neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Because the MPTP model of PD recapitulates many of the known behavioral and pathological features of human PD, we asked whether the striatal cells of mice treated with MPTP in a semi-chronic paradigm enact a transcriptional program that would help elucidate the response to dopamine denervation. Our findings reveal a time-dependent dysregulation in the striatum of a set of genes whose products may impact both the viability and ability to communicate of dopamine neurons in the SN.

Multiple high cell dose injections of normal marrow into newborn jaundiced mice dramatically prolong life despite transient repopulation.

Jaundiced (ja/ja) mice have a severe hemolytic anemia caused by deficiency of the erythroid cytoskeletal protein beta-spectrin. Unless they are transfused, 99% of the mutant mice die after birth. Here, we test a new therapy involving multiple, high cell dose marrow injections into newborn non-ablated recipients. The ja/ja and normal newborn mice were injected intravenously with a total of 8.7 x 10(6) genetically marked +/+ marrow cells/g body weight. Donor and host red blood cells were quantified and the status of the recipients monitored. The jaundiced but not the normal recipients had up to 57% replacement with donor red cells by 9 weeks. The treatment significantly increased red cell counts and extended the average lifespan to 5 months beyond that previously reported for ja/ja mice transfused at birth. Replacement was limited to red cells. The donor cells disappeared in three of five mutant mice alive beyond 27 weeks. Marrow from a 48-month-old ja/ja recipient no longer positive for donor cells was injected into a secondary host. The recipient acquired the blood phenotype of the primary ja/ja host. The possibility that the marker was not well tolerated following multiple cell injections was investigated in normal adult mice injected with a total of 5.3 x 10(6) marrow cells/g body weight. Recipients became chimeric (>38% donor red and white cells) long-term (>12 months). The results indicate donor stem cells (a) prolong life in the jaundiced mice, but (b) do not survive long-term when injected into newborn mice. We conclude that destructive mechanisms may not be limited to ja/ja red cells.