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An unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the C. elegans putative aminophospholipid translocases.

Lyssenko NN, Miteva Y, Gilroy S, Hanna-Rose W, Schlegel RA - BMC Dev. Biol. (2008)

Bottom Line: Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system.Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant.These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. lyssenn@ccf.org

ABSTRACT

Background: P-type ATPases in subfamily IV are exclusively eukaryotic transmembrane proteins that have been proposed to directly translocate the aminophospholipids phosphatidylserine and phosphatidylethanolamine from the exofacial to the cytofacial monolayer of the plasma membrane. Eukaryotic genomes contain many genes encoding members of this subfamily. At present it is unclear why there are so many genes of this kind per organism or what individual roles these genes perform in organism development.

Results: We have systematically investigated expression and developmental function of the six, tat-1 through 6, subfamily IV P-type ATPase genes encoded in the Caenorhabditis elegans genome. tat-5 is the only ubiquitously-expressed essential gene in the group. tat-6 is a poorly-transcribed recent duplicate of tat-5. tat-2 through 4 exhibit tissue-specific developmentally-regulated expression patterns. Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system. The two are also expressed in the uterus, during spermatogenesis and in the fully-formed spermatheca. tat-2 alone is expressed in the pharyngeal gland cells, the excretory system and a few cells of the developing vulva. The expression pattern of tat-3 is almost completely different from those of tat-2 and tat-4. tat-3 expression is detectable in the steroidogenic tissues: the hypodermis and the XXX cells, as well as in most cells of the pharynx (except gland), various tissues of the reproductive system (except uterus and spermatheca) and seam cells. Deletion of tat-1 through 4 individually interferes little or not at all with the regular progression of organism growth and development under normal conditions. However, tat-2 through 4 become essential for reproductive growth during sterol starvation.

Conclusion: tat-5 likely encodes a housekeeping protein that performs the proposed aminophospholipid translocase function routinely. Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant. Expression patterns and the sterol deprivation hypersensitivity deletion phenotype of tat-2 through 4 suggest that these genes carry out subtle metabolic functions, such as fine-tuning sterol metabolism in digestive or steroidogenic tissues. These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

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tat-3 reporter expression pattern. The 5' end of the tat-3 locus, location of the deleted region in tm1275 mutants (bar) and structure of the tat-3 expression cassette (A). tat-3 reporter expression in the pharyngeal-intestinal valve and in muscle and marginal, but not gland, cells of the pharynx in the lcIs471.12 line (B). GFP fluorescence in the muscle and buccal epithelial cells of the pharynx procorpus and in the XXX cells in the lcIs471.4B line (C). tat-3 reporter signals in the rectum and a tail region (D), seam cells and the hypodermis (E), the DTC (F) and the AC (G) of lcIs471.4B animals. GFP staining of the vulva at the late L4 stage in lcIs881.3.2 larvae (H). Reporter expression in the adult lcIs471.4B vulva (I). Cell labels: AC – anchor cell; DTC – distal tip cell; e1 and 2 – buccal epithelial cells; g1 – gland cell; mc – marginal cell; pm2, 5, 6 and 7 – pharyngeal muscle cells; vul – vulval cells; utse – uterine seam cell; XXX – XXX cells. Abbreviations: hn – hypodermal nucleus; pv – pharyngeal-intestinal valve; sn – seam cell nucleus.
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Figure 5: tat-3 reporter expression pattern. The 5' end of the tat-3 locus, location of the deleted region in tm1275 mutants (bar) and structure of the tat-3 expression cassette (A). tat-3 reporter expression in the pharyngeal-intestinal valve and in muscle and marginal, but not gland, cells of the pharynx in the lcIs471.12 line (B). GFP fluorescence in the muscle and buccal epithelial cells of the pharynx procorpus and in the XXX cells in the lcIs471.4B line (C). tat-3 reporter signals in the rectum and a tail region (D), seam cells and the hypodermis (E), the DTC (F) and the AC (G) of lcIs471.4B animals. GFP staining of the vulva at the late L4 stage in lcIs881.3.2 larvae (H). Reporter expression in the adult lcIs471.4B vulva (I). Cell labels: AC – anchor cell; DTC – distal tip cell; e1 and 2 – buccal epithelial cells; g1 – gland cell; mc – marginal cell; pm2, 5, 6 and 7 – pharyngeal muscle cells; vul – vulval cells; utse – uterine seam cell; XXX – XXX cells. Abbreviations: hn – hypodermal nucleus; pv – pharyngeal-intestinal valve; sn – seam cell nucleus.

Mentions: Three integrated and ten extrachromosomal transgenic lines carrying tat-3::nls::gfp cassettes were derived (Figure 5A). Four of these (all of the integrated and one extrachromosomal) were investigated in detail and found to exhibit nearly identical expression patterns. tat-3 reporter signal first appears in embryos in the developing pharynx (data not shown). In the fully formed alimentary system, very strong GFP fluorescence is observed in the muscle, marginal and buccal epithelial cells of the pharynx, the pharyngeal-intestinal valve and, with lesser intensity, the rectal epithelial cells (Figure 5B–D). Seam cells display very strong fluorescence as soon as this lineage becomes established during embryonic development (Figure 5E). In adults, moderate to weak fluorescence seems to arise from the XXX cells, some unidentified cells in the head and tail regions and the hypodermis (Figure 5C and 5E). In the reproductive system, tat-3 reporter expression begins in the distal tip cells (DTC) in L1 and in the anchor cell (AC) in early L3 (Figure 5F and 5G). GFP signal is later visible in the dividing progeny of the vulval precursor cells (VPCs). In late L4, the anchor cell fuses with the uterine seam cell (utse), which does not express the reporter (Figure 5H). The vulval cells continue exhibiting moderate fluorescence into the adulthood (Figure 5H and 5I).


An unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the C. elegans putative aminophospholipid translocases.

Lyssenko NN, Miteva Y, Gilroy S, Hanna-Rose W, Schlegel RA - BMC Dev. Biol. (2008)

tat-3 reporter expression pattern. The 5' end of the tat-3 locus, location of the deleted region in tm1275 mutants (bar) and structure of the tat-3 expression cassette (A). tat-3 reporter expression in the pharyngeal-intestinal valve and in muscle and marginal, but not gland, cells of the pharynx in the lcIs471.12 line (B). GFP fluorescence in the muscle and buccal epithelial cells of the pharynx procorpus and in the XXX cells in the lcIs471.4B line (C). tat-3 reporter signals in the rectum and a tail region (D), seam cells and the hypodermis (E), the DTC (F) and the AC (G) of lcIs471.4B animals. GFP staining of the vulva at the late L4 stage in lcIs881.3.2 larvae (H). Reporter expression in the adult lcIs471.4B vulva (I). Cell labels: AC – anchor cell; DTC – distal tip cell; e1 and 2 – buccal epithelial cells; g1 – gland cell; mc – marginal cell; pm2, 5, 6 and 7 – pharyngeal muscle cells; vul – vulval cells; utse – uterine seam cell; XXX – XXX cells. Abbreviations: hn – hypodermal nucleus; pv – pharyngeal-intestinal valve; sn – seam cell nucleus.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 5: tat-3 reporter expression pattern. The 5' end of the tat-3 locus, location of the deleted region in tm1275 mutants (bar) and structure of the tat-3 expression cassette (A). tat-3 reporter expression in the pharyngeal-intestinal valve and in muscle and marginal, but not gland, cells of the pharynx in the lcIs471.12 line (B). GFP fluorescence in the muscle and buccal epithelial cells of the pharynx procorpus and in the XXX cells in the lcIs471.4B line (C). tat-3 reporter signals in the rectum and a tail region (D), seam cells and the hypodermis (E), the DTC (F) and the AC (G) of lcIs471.4B animals. GFP staining of the vulva at the late L4 stage in lcIs881.3.2 larvae (H). Reporter expression in the adult lcIs471.4B vulva (I). Cell labels: AC – anchor cell; DTC – distal tip cell; e1 and 2 – buccal epithelial cells; g1 – gland cell; mc – marginal cell; pm2, 5, 6 and 7 – pharyngeal muscle cells; vul – vulval cells; utse – uterine seam cell; XXX – XXX cells. Abbreviations: hn – hypodermal nucleus; pv – pharyngeal-intestinal valve; sn – seam cell nucleus.
Mentions: Three integrated and ten extrachromosomal transgenic lines carrying tat-3::nls::gfp cassettes were derived (Figure 5A). Four of these (all of the integrated and one extrachromosomal) were investigated in detail and found to exhibit nearly identical expression patterns. tat-3 reporter signal first appears in embryos in the developing pharynx (data not shown). In the fully formed alimentary system, very strong GFP fluorescence is observed in the muscle, marginal and buccal epithelial cells of the pharynx, the pharyngeal-intestinal valve and, with lesser intensity, the rectal epithelial cells (Figure 5B–D). Seam cells display very strong fluorescence as soon as this lineage becomes established during embryonic development (Figure 5E). In adults, moderate to weak fluorescence seems to arise from the XXX cells, some unidentified cells in the head and tail regions and the hypodermis (Figure 5C and 5E). In the reproductive system, tat-3 reporter expression begins in the distal tip cells (DTC) in L1 and in the anchor cell (AC) in early L3 (Figure 5F and 5G). GFP signal is later visible in the dividing progeny of the vulval precursor cells (VPCs). In late L4, the anchor cell fuses with the uterine seam cell (utse), which does not express the reporter (Figure 5H). The vulval cells continue exhibiting moderate fluorescence into the adulthood (Figure 5H and 5I).

Bottom Line: Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system.Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant.These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. lyssenn@ccf.org

ABSTRACT

Background: P-type ATPases in subfamily IV are exclusively eukaryotic transmembrane proteins that have been proposed to directly translocate the aminophospholipids phosphatidylserine and phosphatidylethanolamine from the exofacial to the cytofacial monolayer of the plasma membrane. Eukaryotic genomes contain many genes encoding members of this subfamily. At present it is unclear why there are so many genes of this kind per organism or what individual roles these genes perform in organism development.

Results: We have systematically investigated expression and developmental function of the six, tat-1 through 6, subfamily IV P-type ATPase genes encoded in the Caenorhabditis elegans genome. tat-5 is the only ubiquitously-expressed essential gene in the group. tat-6 is a poorly-transcribed recent duplicate of tat-5. tat-2 through 4 exhibit tissue-specific developmentally-regulated expression patterns. Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system. The two are also expressed in the uterus, during spermatogenesis and in the fully-formed spermatheca. tat-2 alone is expressed in the pharyngeal gland cells, the excretory system and a few cells of the developing vulva. The expression pattern of tat-3 is almost completely different from those of tat-2 and tat-4. tat-3 expression is detectable in the steroidogenic tissues: the hypodermis and the XXX cells, as well as in most cells of the pharynx (except gland), various tissues of the reproductive system (except uterus and spermatheca) and seam cells. Deletion of tat-1 through 4 individually interferes little or not at all with the regular progression of organism growth and development under normal conditions. However, tat-2 through 4 become essential for reproductive growth during sterol starvation.

Conclusion: tat-5 likely encodes a housekeeping protein that performs the proposed aminophospholipid translocase function routinely. Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant. Expression patterns and the sterol deprivation hypersensitivity deletion phenotype of tat-2 through 4 suggest that these genes carry out subtle metabolic functions, such as fine-tuning sterol metabolism in digestive or steroidogenic tissues. These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

Show MeSH
Related in: MedlinePlus