Differential actions of the proneural genes encoding Mash1 and neurogenins in Nurr1-induced dopamine neuron differentiation.
The steroid receptor-type transcription factor Nurr1 has a crucial role in the development of the mesencephalic dopamine (DA) neurons. Although ectopic expression of Nurr1 in cultured neural precursor cells is sufficient in establishing the DA phenotype, Nurr1-induced DA cells are morphologically and functionally immature, suggesting the necessity of additional factor(s) for full neuronal differentiation. In this study, we demonstrate that neurogenic basic helix-loop-helix (bHLH) factors Mash1, neurogenins (Ngns) and NeuroD play contrasting roles in Nurr1-induced DA neuronal differentiation. Mash1, but not Ngn2, spatially and temporally colocalized with aldehyde dehydrogenase 2 (AHD2), a specific midbrain DA neuronal progenitor marker, in the early embryonic ventral mesencephalon. Forced expression of Mash1 caused immature Nurr1-induced DA cells to differentiate into mature and functional DA neurons as judged by electrophysiological characteristics, release of DA, and expression of presynaptic DA neuronal markers. By contrast, atonal-related bHLHs, represented by Ngn1, Ngn2 and NeuroD, repressed Nurr1-induced expression of DA neuronal markers. Domain-swapping experiments with Mash1 and NeuroD indicated that the helix-loop-helix domain, responsible for mediating dimerization of bHLH transcription factors, imparts the distinct effect. Finally, transient co-transfection of the atonal-related bHLHs with Nurr1 resulted in an E-box-independent repression of Nurr1-induced transcriptional activation of a reporter containing Nurr1-binding element (NL3) as well as a reporter driven by the native tyrosine hydroxylase gene promoter. Taken together, these findings suggest that Mash1 contributes to the generation of DA neurons in cooperation with Nurr1 in the developing midbrain whereas atonal-related bHLH genes inhibit the process.
Park
Chang-Hwan
CH
Department of Microbiology, Hanyang University, Seoul, Korea.
Kang
Jin Sun
JS
Kim
Jae-Sang
JS
Chung
Seungsoo
S
Koh
Jin-Young
JY
Yoon
Eun-Hye
EH
Jo
A Young
AY
Chang
Mi-Yoon
MY
Koh
Hyun-Chul
HC
Hwang
Sejin
S
Suh-Kim
Haeyoung
H
Lee
Yong-Sung
YS
Kim
Kwang-Soo
KS
Lee
Sang-Hun
SH
D000444:Aldehyde Dehydrogenase / Q000235:genetics* / Q000502:physiology; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis / Q000494:pharmacology / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000494:pharmacology / Q000502:physiology*; D004298:Dopamine / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008636:Mesencephalon / Q000196:embryology / Q000254:growth & development / Q000502:physiology; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000494:pharmacology / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000494:pharmacology / Q000502:physiology*; D014446:Tyrosine 3-Monooxygenase / Q000037:antagonists & inhibitors / Q000096:biosynthesis
D000444:Aldehyde Dehydrogenase; D000071396:Aldehyde Dehydrogenase, Mitochondrial; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D004298:Dopamine; D024101:Mitochondrial Proteins; D009419:Nerve Tissue Proteins; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D014157:Transcription Factors; D014446:Tyrosine 3-Monooxygenase; C499318:Ascl1 protein, rat; C539884:Nr4a2 protein, rat; C093564:Neurogenic differentiation factor 1; C505112:Aldh2 protein, rat