Isl1 directly controls a cholinergic neuronal identity in the developing forebrain and spinal cord by forming cell type-specific complexes.
The establishment of correct neurotransmitter characteristics is an essential step of neuronal fate specification in CNS development. However, very little is known about how a battery of genes involved in the determination of a specific type of chemical-driven neurotransmission is coordinately regulated during vertebrate development. Here, we investigated the gene regulatory networks that specify the cholinergic neuronal fates in the spinal cord and forebrain, specifically, spinal motor neurons (MNs) and forebrain cholinergic neurons (FCNs). Conditional inactivation of Isl1, a LIM homeodomain factor expressed in both differentiating MNs and FCNs, led to a drastic loss of cholinergic neurons in the developing spinal cord and forebrain. We found that Isl1 forms two related, but distinct types of complexes, the Isl1-Lhx3-hexamer in MNs and the Isl1-Lhx8-hexamer in FCNs. Interestingly, our genome-wide ChIP-seq analysis revealed that the Isl1-Lhx3-hexamer binds to a suite of cholinergic pathway genes encoding the core constituents of the cholinergic neurotransmission system, such as acetylcholine synthesizing enzymes and transporters. Consistently, the Isl1-Lhx3-hexamer directly coordinated upregulation of cholinergic pathways genes in embryonic spinal cord. Similarly, in the developing forebrain, the Isl1-Lhx8-hexamer was recruited to the cholinergic gene battery and promoted cholinergic gene expression. Furthermore, the expression of the Isl1-Lhx8-complex enabled the acquisition of cholinergic fate in embryonic stem cell-derived neurons. Together, our studies show a shared molecular mechanism that determines the cholinergic neuronal fate in the spinal cord and forebrain, and uncover an important gene regulatory mechanism that directs a specific neurotransmitter identity in vertebrate CNS development.
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America; Department of Otolaryngology-Head and Neck Surgery, Chonnam National University Medical School, Gwangju, Korea.
Hyong-Ho
HH
Cho
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America.
Francesca
F
Cargnin
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America.
Yujin
Y
Kim
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America.
Bora
B
Lee
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America.
Ryuk-Jun
RJ
Kwon
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Korea.
Heejin
H
Nam
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America; Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America.
Rongkun
R
Shen
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America; Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon, United States of America.
Anthony P
AP
Barnes
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America; Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon, United States of America.
Jae W
JW
Lee
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Korea.
Seunghee
S
Lee
Pediatric Neuroscience Research Program, Papé Family Pediatric Research Institute, Department of Pediatrics, Portland, Oregon, United States of America; Vollum Institute, Oregon Health & Science University, Portland, Oregon, United States of America; Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon, United States of America.
Soo-Kyung
SK
Lee
D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D059329:Cholinergic Neurons / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000378:metabolism; D015870:Gene Expression / Q000235:genetics; D053263:Gene Regulatory Networks / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D060850:LIM-Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009046:Motor Neurons / Q000378:metabolism; D016548:Prosencephalon / Q000378:metabolism*; D051381:Rats; D013116:Spinal Cord / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D060850:LIM-Homeodomain Proteins; D014157:Transcription Factors; C063843:insulin gene enhancer binding protein Isl-1