Mouse Anti Chicken Engrail-1 Hybridoma [5H22]

Background: The homeodomain transcription factors Engrailed-1 and Engrailed-2 are required for the survival of mesencephalic dopaminergic (mesDA) neurons in a cell-autonomous and gene-dose-dependent manner. Homozygote mutant mice, deficient of both genes (En1-/-; En2-/-), die at birth and exhibit a loss of all mesDA neurons by mid-gestation. In heterozygote animals (En1+/-; En2-/-), which are viable and fertile, postnatal maintenance of the nigrostriatal dopaminergic system is afflicted, leading to a progressive degeneration specific to this subpopulation and Parkinson's disease-like molecular and behavioral deficits. Results: In this work, we show that the dose of Engrailed is inversely correlated to the expression level of the pan-neurotrophin receptor gene P75(NTR) (Ngfr). Loss of mesDA neurons in the Engrailed-null mutant embryos is caused by elevated expression of this neurotrophin receptor: Unusually, in this case, the cell death signal of P75(NTR) is mediated by suppression of Erk1/2 (extracellular-signal-regulated kinase 1/2) activity. The reduction in expression of Engrailed, possibly related to the higher levels of P75(NTR), also decreases mitochondrial stability. In particular, the dose of Engrailed determines the sensitivity to cell death induced by the classic Parkinson-model toxin MPTP and to inhibition of the anti-apoptotic members of the Bcl-2 family of proteins. Conclusion: Our study links the survival function of the Engrailed genes in developing mesDA neurons to the regulation of P75(NTR) and the sensitivity of these neurons to mitochondrial insult. The similarities to the disease etiology in combination with the nigral phenotype of En1+/-; En2-/- mice suggests that haplotype variations in the Engrailed genes and/or P75(NTR) that alter their expression levels could, in part, determine susceptibility to Parkinson's disease.

The brain vesicles that are formed at an early stage of neural development are the fundamentals of the brain plan. Heterotopic transplantation revealed that the diencephalon could change its fate when juxtaposed to the isthmus (mes-metencephalic boundary), which indicated that the isthmus functions as an organizer for the mesencephalon and metencephalon. Fgf8 is identified as an isthmus organizing signal. Misexpression of Fgf8a and Fgf8b indicated that a strong Fgf8 signal organizes cerebellar development. The transcription factors define the fate of the region. Overlapping expression of Otx2, En1 and Pax2 may define the mesencephalic region and additional expression of Pax3/7 may instruct the mesencephalic region to differentiate into the tectum. The di-mesencephalic boundary is determined by repressive interaction between Pax6 and En1/Pax2 and the mes-metencephalic boundary is defined by repressive interaction between Otx2 and Gbx2. Fgf8 is induced at the border of the Otx2 and Gbx2 expression domain, overlapping with Gbx2 expression.