Limits...
The Evolutionarily Conserved LIM Homeodomain Protein LIM-4/LHX6 Specifies the Terminal Identity of a Cholinergic and Peptidergic C. elegans Sensory/Inter/Motor Neuron-Type.

Kim J, Yeon J, Choi SK, Huh YH, Fang Z, Park SJ, Kim MO, Ryoo ZY, Kang K, Kweon HS, Jeon WB, Li C, Kim K - PLoS Genet. (2015)

Bottom Line: Two human LIM-4 orthologs, LHX6 and LHX8, functionally substitute for LIM-4 in C. elegans.Furthermore, C. elegans LIM-4 or human LHX6 can induce cholinergic and peptidergic characteristics in the human neuronal cell lines.Our results indicate that the evolutionarily conserved LIM-4/LHX6 homeodomain proteins function in generation of precise neuronal subtypes.

View Article: PubMed Central - PubMed

Affiliation: Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Korea.

ABSTRACT
The expression of specific transcription factors determines the differentiated features of postmitotic neurons. However, the mechanism by which specific molecules determine neuronal cell fate and the extent to which the functions of transcription factors are conserved in evolution are not fully understood. In C. elegans, the cholinergic and peptidergic SMB sensory/inter/motor neurons innervate muscle quadrants in the head and control the amplitude of sinusoidal movement. Here we show that the LIM homeobox protein LIM-4 determines neuronal characteristics of the SMB neurons. In lim-4 mutant animals, expression of terminal differentiation genes, such as the cholinergic gene battery and the flp-12 neuropeptide gene, is completely abolished and thus the function of the SMB neurons is compromised. LIM-4 activity promotes SMB identity by directly regulating the expression of the SMB marker genes via a distinct cis-regulatory motif. Two human LIM-4 orthologs, LHX6 and LHX8, functionally substitute for LIM-4 in C. elegans. Furthermore, C. elegans LIM-4 or human LHX6 can induce cholinergic and peptidergic characteristics in the human neuronal cell lines. Our results indicate that the evolutionarily conserved LIM-4/LHX6 homeodomain proteins function in generation of precise neuronal subtypes.

No MeSH data available.


Related in: MedlinePlus

Expression of a flp-12 neuropeptide reporter is abolished in the SMB neurons of lim-4 mutants.(A) Schematic drawing of the SMB neurons in C. elegans. Four cell bodies are located in the head (DL: dorsal left, DR: dorsal right, VL: ventral left, VR: ventral right) and their processes run in sublateral cords to the tail. (B) Expression of the flp-12 neuropeptide reporter is abolished specifically in the SMB neurons of lim-4 mutants. GFP expression in ynIs25 integrated strains is observed in the SMB and SDQ(L/R) neurons of wild-type adult (left column) or L1 larval (right column) stage animals while GFP expression in the SMB neurons is not detected in lim-4  mutant alleles (lsk5, ky403). Faint expression of the flp-12p::gfp reporter in the SAA and AVH/J neurons of L1 larvae is not altered in lim-4 mutants. Anterior is at left in all images. Scale bars: 20 μm. (C) Genomic structure of lim-4 (left) and schematic structure of the LIM domain of LIM-4 (right). The sequence alignment of part of the LIM domain of C. elegans LIM-4 and human LHX6 and LHX8 is shown. Identical residues in at least two proteins are shown in red. Molecular lesions of lim-4 mutant alleles are indicated. *Mutation in ky403 was previously reported [14]. LIM domain and homeodomain are labeled in green and in yellow, respectively.
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pgen.1005480.g001: Expression of a flp-12 neuropeptide reporter is abolished in the SMB neurons of lim-4 mutants.(A) Schematic drawing of the SMB neurons in C. elegans. Four cell bodies are located in the head (DL: dorsal left, DR: dorsal right, VL: ventral left, VR: ventral right) and their processes run in sublateral cords to the tail. (B) Expression of the flp-12 neuropeptide reporter is abolished specifically in the SMB neurons of lim-4 mutants. GFP expression in ynIs25 integrated strains is observed in the SMB and SDQ(L/R) neurons of wild-type adult (left column) or L1 larval (right column) stage animals while GFP expression in the SMB neurons is not detected in lim-4 mutant alleles (lsk5, ky403). Faint expression of the flp-12p::gfp reporter in the SAA and AVH/J neurons of L1 larvae is not altered in lim-4 mutants. Anterior is at left in all images. Scale bars: 20 μm. (C) Genomic structure of lim-4 (left) and schematic structure of the LIM domain of LIM-4 (right). The sequence alignment of part of the LIM domain of C. elegans LIM-4 and human LHX6 and LHX8 is shown. Identical residues in at least two proteins are shown in red. Molecular lesions of lim-4 mutant alleles are indicated. *Mutation in ky403 was previously reported [14]. LIM domain and homeodomain are labeled in green and in yellow, respectively.

Mentions: The SMB multimodal sensory/inter/motor neurons consist of two pairs of neurons that are located in the head and innervate the head neck muscles (Fig 1A). Their processes, which run in ventral or dorsal sublateral cords to the tail and have electric and chemical synaptic contacts to other neurons in the head, were proposed to sense the stretch of body and regulate head locomotion [11]. In fact, laser ablation of the SMB neurons caused increased reversal frequency and wave amplitude of forward locomotion [12]. These neurons utilize at least two neurotransmitters, acetylcholine and a FMRFamide-related peptide, FLP-12 [5, 13]. Genes or molecules that are pivotal for the generation or differentiation of these SMB neurons have not been identified.


The Evolutionarily Conserved LIM Homeodomain Protein LIM-4/LHX6 Specifies the Terminal Identity of a Cholinergic and Peptidergic C. elegans Sensory/Inter/Motor Neuron-Type.

Kim J, Yeon J, Choi SK, Huh YH, Fang Z, Park SJ, Kim MO, Ryoo ZY, Kang K, Kweon HS, Jeon WB, Li C, Kim K - PLoS Genet. (2015)

Expression of a flp-12 neuropeptide reporter is abolished in the SMB neurons of lim-4 mutants.(A) Schematic drawing of the SMB neurons in C. elegans. Four cell bodies are located in the head (DL: dorsal left, DR: dorsal right, VL: ventral left, VR: ventral right) and their processes run in sublateral cords to the tail. (B) Expression of the flp-12 neuropeptide reporter is abolished specifically in the SMB neurons of lim-4 mutants. GFP expression in ynIs25 integrated strains is observed in the SMB and SDQ(L/R) neurons of wild-type adult (left column) or L1 larval (right column) stage animals while GFP expression in the SMB neurons is not detected in lim-4  mutant alleles (lsk5, ky403). Faint expression of the flp-12p::gfp reporter in the SAA and AVH/J neurons of L1 larvae is not altered in lim-4 mutants. Anterior is at left in all images. Scale bars: 20 μm. (C) Genomic structure of lim-4 (left) and schematic structure of the LIM domain of LIM-4 (right). The sequence alignment of part of the LIM domain of C. elegans LIM-4 and human LHX6 and LHX8 is shown. Identical residues in at least two proteins are shown in red. Molecular lesions of lim-4 mutant alleles are indicated. *Mutation in ky403 was previously reported [14]. LIM domain and homeodomain are labeled in green and in yellow, respectively.
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Related In: Results  -  Collection

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pgen.1005480.g001: Expression of a flp-12 neuropeptide reporter is abolished in the SMB neurons of lim-4 mutants.(A) Schematic drawing of the SMB neurons in C. elegans. Four cell bodies are located in the head (DL: dorsal left, DR: dorsal right, VL: ventral left, VR: ventral right) and their processes run in sublateral cords to the tail. (B) Expression of the flp-12 neuropeptide reporter is abolished specifically in the SMB neurons of lim-4 mutants. GFP expression in ynIs25 integrated strains is observed in the SMB and SDQ(L/R) neurons of wild-type adult (left column) or L1 larval (right column) stage animals while GFP expression in the SMB neurons is not detected in lim-4 mutant alleles (lsk5, ky403). Faint expression of the flp-12p::gfp reporter in the SAA and AVH/J neurons of L1 larvae is not altered in lim-4 mutants. Anterior is at left in all images. Scale bars: 20 μm. (C) Genomic structure of lim-4 (left) and schematic structure of the LIM domain of LIM-4 (right). The sequence alignment of part of the LIM domain of C. elegans LIM-4 and human LHX6 and LHX8 is shown. Identical residues in at least two proteins are shown in red. Molecular lesions of lim-4 mutant alleles are indicated. *Mutation in ky403 was previously reported [14]. LIM domain and homeodomain are labeled in green and in yellow, respectively.
Mentions: The SMB multimodal sensory/inter/motor neurons consist of two pairs of neurons that are located in the head and innervate the head neck muscles (Fig 1A). Their processes, which run in ventral or dorsal sublateral cords to the tail and have electric and chemical synaptic contacts to other neurons in the head, were proposed to sense the stretch of body and regulate head locomotion [11]. In fact, laser ablation of the SMB neurons caused increased reversal frequency and wave amplitude of forward locomotion [12]. These neurons utilize at least two neurotransmitters, acetylcholine and a FMRFamide-related peptide, FLP-12 [5, 13]. Genes or molecules that are pivotal for the generation or differentiation of these SMB neurons have not been identified.

Bottom Line: Two human LIM-4 orthologs, LHX6 and LHX8, functionally substitute for LIM-4 in C. elegans.Furthermore, C. elegans LIM-4 or human LHX6 can induce cholinergic and peptidergic characteristics in the human neuronal cell lines.Our results indicate that the evolutionarily conserved LIM-4/LHX6 homeodomain proteins function in generation of precise neuronal subtypes.

View Article: PubMed Central - PubMed

Affiliation: Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Korea.

ABSTRACT
The expression of specific transcription factors determines the differentiated features of postmitotic neurons. However, the mechanism by which specific molecules determine neuronal cell fate and the extent to which the functions of transcription factors are conserved in evolution are not fully understood. In C. elegans, the cholinergic and peptidergic SMB sensory/inter/motor neurons innervate muscle quadrants in the head and control the amplitude of sinusoidal movement. Here we show that the LIM homeobox protein LIM-4 determines neuronal characteristics of the SMB neurons. In lim-4 mutant animals, expression of terminal differentiation genes, such as the cholinergic gene battery and the flp-12 neuropeptide gene, is completely abolished and thus the function of the SMB neurons is compromised. LIM-4 activity promotes SMB identity by directly regulating the expression of the SMB marker genes via a distinct cis-regulatory motif. Two human LIM-4 orthologs, LHX6 and LHX8, functionally substitute for LIM-4 in C. elegans. Furthermore, C. elegans LIM-4 or human LHX6 can induce cholinergic and peptidergic characteristics in the human neuronal cell lines. Our results indicate that the evolutionarily conserved LIM-4/LHX6 homeodomain proteins function in generation of precise neuronal subtypes.

No MeSH data available.


Related in: MedlinePlus