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Foxn1[Cre] Expression in the Male Germline

View Article: PubMed Central - PubMed

ABSTRACT

Foxn1 (forkhead box N1), also known as the nude gene or winged-helix nude (Whn), is a forkhead transcription factor thought to be restricted to keratinocytes in the skin and thymus. Consistent with this tissue distribution, spontaneous or targeted mutation of Foxn1 results in the absence of both hair and a thymus. Genetic manipulation of the Foxn1 locus thus represents a powerful tool for tissue specific gene control in the skin and thymus, and tools such as Cre recombinase under control of the Foxn1 locus are widely used for this purpose. Unexpectedly, we show that Foxn1[Cre] exhibits unexpected activity in male germ cells, resulting in ubiquitous targeting of loxP-flanked alleles in all tissues in offspring from Foxn1[Cre] expressing male mice. Inheritance of recombined loxP alleles occurs independently of Cre inheritance (i.e., offspring lacking Cre nonetheless exhibit recombined alleles), suggesting that Foxn1[Cre] induced recombination in male germ cells must occur prior to meiosis in diploid germ cells. Together with previously published data, our results show that Foxn1, and alleles under its control, are expressed in the pre-meiotic male germline, revealing a new tool for germline targeting of genes, and raising important concerns for gender selection when using Foxn1 regulatory elements.

No MeSH data available.


Related in: MedlinePlus

A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding.A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding. For each tissue, a 10x (top) or 40x (bottom) perspective is shown. Top left is thymic tissue from a conditional reporter mouse (Rosa26 knock-in stop/floxGfp) without Cre. DAPI (blue) indicates nuclei. All other panels are tissues from Cre- offspring of a male Foxn1[Cre]+Rosa[stop/floxGfp]+ x C57BL/6 female cross. All panels have the same exposure time for DAPI or for Gfp (at each magnification). All cells were Gfp+ in all tissues examined. Representative results are shown; the results were confirmed in tissues from 2–5 individual mice, depending on the tissue used.
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pone.0166967.g003: A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding.A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding. For each tissue, a 10x (top) or 40x (bottom) perspective is shown. Top left is thymic tissue from a conditional reporter mouse (Rosa26 knock-in stop/floxGfp) without Cre. DAPI (blue) indicates nuclei. All other panels are tissues from Cre- offspring of a male Foxn1[Cre]+Rosa[stop/floxGfp]+ x C57BL/6 female cross. All panels have the same exposure time for DAPI or for Gfp (at each magnification). All cells were Gfp+ in all tissues examined. Representative results are shown; the results were confirmed in tissues from 2–5 individual mice, depending on the tissue used.

Mentions: The above findings suggest that Cre expression under the control of the Foxn1 locus results in promiscuous recombination of conditional loxP alleles when Cre is carried by the male parent, independent of Cre inheritance or Foxn1 expression in somatic tissue. To extend these findings, we examined a panel of tissues derived from Cre-negative offspring of Foxn1[Cre] male X Rosa[mTmG] female crosses. Fig 3 shows representative results from thymus, intestine, heart, brain, kidney, liver, or skin from a Foxn1[Cre]-negative Rosa[mTmG]-positive mouse; the activated Gfp reporter was seen in all cells in all tissues examined. This was not the case in Foxn1[Cre]-negative Rosa[mTmG]-positive offspring of female mice carrying the Foxn1[Cre] gene (not shown), as expected. Together, these findings substantiate our conclusion that Cre expression directed by Foxn1 regulatory sequences occurs in diploid male germ cells, but not in the female germline.


Foxn1[Cre] Expression in the Male Germline
A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding.A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding. For each tissue, a 10x (top) or 40x (bottom) perspective is shown. Top left is thymic tissue from a conditional reporter mouse (Rosa26 knock-in stop/floxGfp) without Cre. DAPI (blue) indicates nuclei. All other panels are tissues from Cre- offspring of a male Foxn1[Cre]+Rosa[stop/floxGfp]+ x C57BL/6 female cross. All panels have the same exposure time for DAPI or for Gfp (at each magnification). All cells were Gfp+ in all tissues examined. Representative results are shown; the results were confirmed in tissues from 2–5 individual mice, depending on the tissue used.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5120802&req=5

pone.0166967.g003: A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding.A conditional reporter is activated in all cells and tissues in Cre- offspring of Cre+reporter+ male x C57BL/6 female breeding. For each tissue, a 10x (top) or 40x (bottom) perspective is shown. Top left is thymic tissue from a conditional reporter mouse (Rosa26 knock-in stop/floxGfp) without Cre. DAPI (blue) indicates nuclei. All other panels are tissues from Cre- offspring of a male Foxn1[Cre]+Rosa[stop/floxGfp]+ x C57BL/6 female cross. All panels have the same exposure time for DAPI or for Gfp (at each magnification). All cells were Gfp+ in all tissues examined. Representative results are shown; the results were confirmed in tissues from 2–5 individual mice, depending on the tissue used.
Mentions: The above findings suggest that Cre expression under the control of the Foxn1 locus results in promiscuous recombination of conditional loxP alleles when Cre is carried by the male parent, independent of Cre inheritance or Foxn1 expression in somatic tissue. To extend these findings, we examined a panel of tissues derived from Cre-negative offspring of Foxn1[Cre] male X Rosa[mTmG] female crosses. Fig 3 shows representative results from thymus, intestine, heart, brain, kidney, liver, or skin from a Foxn1[Cre]-negative Rosa[mTmG]-positive mouse; the activated Gfp reporter was seen in all cells in all tissues examined. This was not the case in Foxn1[Cre]-negative Rosa[mTmG]-positive offspring of female mice carrying the Foxn1[Cre] gene (not shown), as expected. Together, these findings substantiate our conclusion that Cre expression directed by Foxn1 regulatory sequences occurs in diploid male germ cells, but not in the female germline.

View Article: PubMed Central - PubMed

ABSTRACT

Foxn1 (forkhead box N1), also known as the nude gene or winged-helix nude (Whn), is a forkhead transcription factor thought to be restricted to keratinocytes in the skin and thymus. Consistent with this tissue distribution, spontaneous or targeted mutation of Foxn1 results in the absence of both hair and a thymus. Genetic manipulation of the Foxn1 locus thus represents a powerful tool for tissue specific gene control in the skin and thymus, and tools such as Cre recombinase under control of the Foxn1 locus are widely used for this purpose. Unexpectedly, we show that Foxn1[Cre] exhibits unexpected activity in male germ cells, resulting in ubiquitous targeting of loxP-flanked alleles in all tissues in offspring from Foxn1[Cre] expressing male mice. Inheritance of recombined loxP alleles occurs independently of Cre inheritance (i.e., offspring lacking Cre nonetheless exhibit recombined alleles), suggesting that Foxn1[Cre] induced recombination in male germ cells must occur prior to meiosis in diploid germ cells. Together with previously published data, our results show that Foxn1, and alleles under its control, are expressed in the pre-meiotic male germline, revealing a new tool for germline targeting of genes, and raising important concerns for gender selection when using Foxn1 regulatory elements.

No MeSH data available.


Related in: MedlinePlus