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

LIM-4 regulates expression of the terminally differentiated markers in the SMB neurons.(A) Schematic drawing of expressed genes in the SMB neurons; odr-2 (GPI-anchored cell surface protein), trp-1 (TRPC channel), unc-17 (VAChT), cho-1 (ChT), and flp-12 (neuropeptide) (B-D) Expression of the indicated reporter constructs is shown in wild-type (left column) or lim-4(ky403) mutant (right column) animals. Merged images with the ceh-17p::mCherry reporter expression in the SIA neurons (shown in red) were shown for trp-1, unc-17, cho-1, rgef-1, or unc-119 promoter reporter for help in identification of the SMB neurons (see S3 Fig). Images are derived from z-stacks of confocal microscopy images while images in the upper-left boxed regions are single focal plane confocal microscopy images. Quantitative analysis of these phenotypes is shown in Table 1. Anterior is to the left. Scale bar: 50 μm.
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pgen.1005480.g002: LIM-4 regulates expression of the terminally differentiated markers in the SMB neurons.(A) Schematic drawing of expressed genes in the SMB neurons; odr-2 (GPI-anchored cell surface protein), trp-1 (TRPC channel), unc-17 (VAChT), cho-1 (ChT), and flp-12 (neuropeptide) (B-D) Expression of the indicated reporter constructs is shown in wild-type (left column) or lim-4(ky403) mutant (right column) animals. Merged images with the ceh-17p::mCherry reporter expression in the SIA neurons (shown in red) were shown for trp-1, unc-17, cho-1, rgef-1, or unc-119 promoter reporter for help in identification of the SMB neurons (see S3 Fig). Images are derived from z-stacks of confocal microscopy images while images in the upper-left boxed regions are single focal plane confocal microscopy images. Quantitative analysis of these phenotypes is shown in Table 1. Anterior is to the left. Scale bar: 50 μm.

Mentions: To determine the extent to which LIM-4 regulates gene expression in the SMB neurons, we examined additional SMB terminal differentiation genes, including odr-2 GPI-anchored cell surface protein [17], trp-1 TRPC channel [18], and cholinergic markers such as unc-17 vesicular acetylcholine transporter (VAChT) [19] and cho-1 choline transporter (ChT) (Fig 2A) [20]. In order to locate the SMB cell bodies, we used expression of ceh-17p::dsRed in the cell bodies of SIAV as a marker that is directly adjacent to the cell bodies of SMBD (S3 Fig) [21]. None of the SMB specific or cholinergic markers were expressed in the SMB neurons of lim-4 mutants while expression in other neuron types was generally not affected (Fig 2B and 2C; Table 1). We next tested expression of two well-characterized pan-neuronal gene markers, rgef-1 Ras guanine nucleotide releasing protein and unc-119 chaperone [6, 7]. Expression of these pan-neuronal genes was not altered in the SMB neurons of lim-4 mutants (Fig 2D; Table 1), indicating that the SMB cells may retain neuronal properties.


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)

LIM-4 regulates expression of the terminally differentiated markers in the SMB neurons.(A) Schematic drawing of expressed genes in the SMB neurons; odr-2 (GPI-anchored cell surface protein), trp-1 (TRPC channel), unc-17 (VAChT), cho-1 (ChT), and flp-12 (neuropeptide) (B-D) Expression of the indicated reporter constructs is shown in wild-type (left column) or lim-4(ky403) mutant (right column) animals. Merged images with the ceh-17p::mCherry reporter expression in the SIA neurons (shown in red) were shown for trp-1, unc-17, cho-1, rgef-1, or unc-119 promoter reporter for help in identification of the SMB neurons (see S3 Fig). Images are derived from z-stacks of confocal microscopy images while images in the upper-left boxed regions are single focal plane confocal microscopy images. Quantitative analysis of these phenotypes is shown in Table 1. Anterior is to the left. Scale bar: 50 μm.
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Related In: Results  -  Collection

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pgen.1005480.g002: LIM-4 regulates expression of the terminally differentiated markers in the SMB neurons.(A) Schematic drawing of expressed genes in the SMB neurons; odr-2 (GPI-anchored cell surface protein), trp-1 (TRPC channel), unc-17 (VAChT), cho-1 (ChT), and flp-12 (neuropeptide) (B-D) Expression of the indicated reporter constructs is shown in wild-type (left column) or lim-4(ky403) mutant (right column) animals. Merged images with the ceh-17p::mCherry reporter expression in the SIA neurons (shown in red) were shown for trp-1, unc-17, cho-1, rgef-1, or unc-119 promoter reporter for help in identification of the SMB neurons (see S3 Fig). Images are derived from z-stacks of confocal microscopy images while images in the upper-left boxed regions are single focal plane confocal microscopy images. Quantitative analysis of these phenotypes is shown in Table 1. Anterior is to the left. Scale bar: 50 μm.
Mentions: To determine the extent to which LIM-4 regulates gene expression in the SMB neurons, we examined additional SMB terminal differentiation genes, including odr-2 GPI-anchored cell surface protein [17], trp-1 TRPC channel [18], and cholinergic markers such as unc-17 vesicular acetylcholine transporter (VAChT) [19] and cho-1 choline transporter (ChT) (Fig 2A) [20]. In order to locate the SMB cell bodies, we used expression of ceh-17p::dsRed in the cell bodies of SIAV as a marker that is directly adjacent to the cell bodies of SMBD (S3 Fig) [21]. None of the SMB specific or cholinergic markers were expressed in the SMB neurons of lim-4 mutants while expression in other neuron types was generally not affected (Fig 2B and 2C; Table 1). We next tested expression of two well-characterized pan-neuronal gene markers, rgef-1 Ras guanine nucleotide releasing protein and unc-119 chaperone [6, 7]. Expression of these pan-neuronal genes was not altered in the SMB neurons of lim-4 mutants (Fig 2D; Table 1), indicating that the SMB cells may retain neuronal properties.

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