ミミズはどうやって腸を発達させるの?(How do worms develop their gut?)

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2022-12-07 カリフォルニア大学リバーサイド校(UCR)

線虫ではたくさんあるGATA因子が、C. angariaではたった1つの因子であることがわかった。このたった1つの因子、ELT-3は、実は線虫にも存在するのですが、同じ機能は持っていない。
線虫ではELT-3因子はストレス反応に関与することが知られており、その機能は他の2つの遺伝子、END-1とEND-3の機能に置き換わっている。ELT-3を欠失させたC.angariaと同様に、END-1とEND-3の両方が欠落した場合、線虫の腸は形成されなくなる。

<関連情報>

GATA因子ELT-3は、Caenorhabditis angariaの内胚葉を祖先遺伝子ネットワークで規定する The GATA factor ELT-3 specifies endoderm in Caenorhabditis angaria in an ancestral gene network

Gina Broitman-Maduro,Simo Sun,Taisei Kikuch,Morris F. Maduro
Development  Published:24 October 2022
DOI:https://doi.org/10.1242/dev.200984

The E blastomere, the core endoderm gene network, and GATA factor conservation in Caenorhabditis. (A) The E cell, shown at the eight-cell stage, gives rise to 20 descendants that form the juvenile intestine, shown in a larva. The nuclei of E and its descendants are shaded green. The remainder of the digestive tract is also shown. ant., anterior; post., posterior. (B) Diagram of the endoderm specification network from C. elegans (Maduro, 2017). The factors that are absent in more distant relatives of C. elegans are shaded in blue. Black lines indicate strong regulatory interactions, and gray lines indicate weaker interactions. (C) Alignment of the DBDs (C4 zinc finger and basic domain) of the canonical GATA factors in C. elegans and C. angaria. The coloured blocks were generated by MView Multiple Sequence Alignment (https://www.ebi.ac.uk/Tools/msa/mview/). (D) RAxML-NG tree of the DBDs shown in C generated using CIPRES Gateway (https://www.phylo.org/), similar to trees made in a prior work (Eurmsirilerd and Maduro, 2020). The C. elegans genome contains two additional embryonic GATA factors, elt-4, which is a partial duplication of elt-2 that lacks function, and elt-6, a paralogue of elt-5 (Koh and Rothman, 2001; Fukushige et al., 2003). (E) Phylogeny of C. elegans with two outgroup species, Diploscapter coronatus and Heterorhabditis bacteriophora, based on previously published work and the most recent phylogeny available from The Caenorhabditis Genomes Project (Félix et al., 2014; Slos et al., 2017; Stevens et al., 2019; Stevens et al., 2020). For C. uteleia, the elt-2 orthologue is CUTEL.g25177 and the elt-3 orthologues are CUTEL.g19098, CUTEL.g19099, CUTEL.g14171 and CUTEL.g17053 (assembly JU2585_v1 from The Caenorhabditis Genomes Project). For C. portoensis, the elt-2 orthologue is CPORT.g4338 and the elt-3 orthologue is CPORT.g6550 (assembly EG5626_v1 from The Caenorhabditis Genomes Project). All remaining orthologues were identified previously (Eurmsirilerd and Maduro, 2020; Maduro, 2020). Species studied in this work are in bold.

ABSTRACT

Endoderm specification in Caenorhabditis elegans occurs through a network in which maternally provided SKN-1/Nrf, with additional input from POP-1/TCF, activates the GATA factor cascade MED-1,2→END-1,3→ELT-2,7. Orthologues of the MED, END and ELT-7 factors are found only among nematodes closely related to C. elegans, raising the question of how gut is specified in their absence in more distant species in the genus. We find that the C. angaria, C. portoensis and C. monodelphis orthologues of the GATA factor gene elt-3 are expressed in the early E lineage, just before their elt-2 orthologues. In C. angaria, Can-pop-1(RNAi), Can-elt-3(RNAi) and a Can-elt-3 null mutation result in a penetrant ‘gutless’ phenotype. Can-pop-1 is necessary for Can-elt-3 activation, showing that it acts upstream. Forced early E lineage expression of Can-elt-3 in C. elegans can direct the expression of a Can-elt-2 transgene and rescue an elt-7 end-1 end-3; elt-2 quadruple mutant strain to viability. Our results demonstrate an ancestral mechanism for gut specification and differentiation in Caenorhabditis involving a simpler POP-1→ELT-3→ELT-2 gene network.

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