A lesson from flex: consider the Y chromosome when assessing Drosophila sex-specific lethals

Bhattacharya et al. (Bhattacharya, A., Sudha, S., Chandra, H. S. and Steward, R. (1999) Development 126, 5485–5493) reported that loss-of-function mutations in the flex (female-specific lethal on X) gene caused female-specific lethality because flex(+) acts as a positive regulator of the master switch gene Sex lethal (Sxl). Sxl is essential for female development. Key to their conclusion was the ability of flex mutations to suppress the male lethality caused by Sxl(M) mutations, which inappropriately activate Sxl female-specific expression. Here we report our contrary findings that flex mutations fail to suppress even the weakest Sxl(M)alleles, arguing against the proposed regulatory relationship between flex and Sxl. Instead we show that the lethal flex phenotype depends on the absence of a Y chromosome, not on the presence of two X chromosomes. flex lethality is caused by a defect in the functioning of the X-linked rDNA locus called bobbed, since this defect is complemented by the corresponding wild-type rDNA complex on the Y.

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A FEMALE-SPECIFIC LETHAL LESION IN AN X-LINKED POSITIVE REGULATOR OF THE DROSOPHILA SEX DETERMINATION GENE, SEX-LETHAL

Genetics ◽

10.1093/genetics/113.3.641 ◽

1986 ◽

Vol 113 (3) ◽

pp. 641-663

Author(s):

Thomas W Cline

Keyword(s):

Sex Determination ◽

Dosage Compensation ◽

Loss Of Function ◽

Female Development ◽

Lethal Effects ◽

Larval Stages ◽

Positive Regulator ◽

Sexual Phenotype ◽

Activity State ◽

Female Specific

ABSTRACT Characterization of a partial-loss-of-function, female-specific lethal mutation has identified an X-linked genetic element (1-34.3; 10B4) that functions as a positive regulator of Sxl, a central gene controlling sex determination in Drosophila melanogaster. The name, sisterless-a, was chosen both to suggest functional similarities that exist between this gene and another positive regulator of Sxl, the maternally acting gene daughterless (da), and also to highlight an important difference; namely, that in contrast to da, it is the zygotic rather than maternal functioning of sis-a that is involved in its interaction with Sxl. As with da, the female-specific lethal phenotype of sis-a is suppressed both by SxlM #1, a gain-of-function mutant allele of the target gene, and, to a lesser extent, by a duplication of Sxl +. Mutations at sis-a, da and Sxl display female-specific dominant synergism, each enhancing the others' lethal effects. The allele specificity with respect to Sxl of these dominant interactions indicates that sis-a and da affect the same aspect of Sxl regulation. As with previous studies of da and Sxl, the masculinizing effects of loss of sis-a function are generally obscured by lethal effects, presumably related to upsets in dosage compensation. The masculinizing effects can be dissociated from lethal effects by analysis of triploid intersexes (XX AAA) or by analysis of diploid females who are also mutant for autosomal genes known to be required for the transcriptional hyperactivation associated with dosage compensation in males. Analysis of foreleg development shows that intersexuality generated by sis-a is of the mosaic type: At the level of individual cells, only male or female development is observed, never an intermediate sexual phenotype characteristic of true intersexes. Sexual development of diplo-X germline and somatic clones of sis-a tissue generated by mitotic recombination during larval stages is normal, as is the sexual phenotype of homozygous sis-a escapers. Considered in their totality, these results indicate that sis-a functions early in development to help establish the activity state of Sxl and thereby initiate the sexual pathway commitment, rather than functioning later in the processes by which Sxl maintains and expresses the sex determination decision.

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The Role of Discoidin Domain Receptor 2 in Tooth Development

Journal of Dental Research ◽

10.1177/0022034519892563 ◽

2019 ◽

Vol 99 (2) ◽

pp. 214-222

Author(s):

F.F. Mohamed ◽

C. Ge ◽

A. Binrayes ◽

R.T. Franceschi

Keyword(s):

Expression Pattern ◽

Alveolar Bone ◽

Tooth Development ◽

Tyrosine Kinase Receptor ◽

Loss Of Function ◽

Wild Type ◽

Specific Expression ◽

Tooth Formation ◽

Discoidin Domain Receptor ◽

Discoidin Domain Receptor 2

Collagen signaling is critical for proper bone and tooth formation. Discoidin domain receptor 2 (DDR2) is a collagen-activated tyrosine kinase receptor shown to be essential for skeletal development. Patients with loss of function mutations in DDR2 develop spondylo-meta-epiphyseal dysplasia (SMED), a rare, autosomal recessive disorder characterized by short stature, short limbs, and craniofacial anomalies. A similar phenotype was observed in Ddr2-deficient mice, which exhibit dwarfism and defective bone formation in the axial, appendicular, and cranial skeletons. However, it is not known if Ddr2 has a role in tooth formation. We first defined the expression pattern of Ddr2 during tooth formation using Ddr2-LacZ knock-in mice. Ddr2 expression was detected in the dental follicle/sac and dental papilla mesenchyme of developing teeth and in odontoblasts and the periodontal ligament (PDL) of adults. No LacZ staining was detected in wild-type littermates. This Ddr2 expression pattern suggests a potential role in the tooth and surrounding periodontium. To uncover the function of Ddr2, we used Ddr2 slie/slie mice, which contain a spontaneous 150-kb deletion in the Ddr2 locus to produce an effective null. In comparison with wild-type littermates, Ddr2 slie/slie mice displayed disproportional tooth size (decreased root/crown ratio), delayed tooth root development, widened PDL space, and interradicular alveolar bone defects. Ddr2 slie/slie mice also had abnormal collagen content associated with upregulation of periostin levels within the PDL. The delayed root formation and periodontal abnormalities may be related to defects in RUNX2-dependent differentiation of odontoblasts and osteoblasts; RUNX2-S319-P was reduced in PDLs from Ddr2 slie/slie mice, and deletion of Ddr2 in primary cell cultures from dental pulp and PDL inhibited differentiation of cells to odontoblasts or osteoblasts, respectively. Together, our studies demonstrate odontoblast- and PDL-specific expression of Ddr2 in mature and immature teeth, as well as indicate that DDR2 signaling is important for normal tooth formation and maintenance of the surrounding periodontium.

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spiel ohne grenzen/pou2is required for zebrafish hindbrain segmentation

Development ◽

10.1242/dev.129.7.1645 ◽

2002 ◽

Vol 129 (7) ◽

pp. 1645-1655 ◽

Cited By ~ 1

Author(s):

Giselbert Hauptmann ◽

Heinz-Georg Belting ◽

Uta Wolke ◽

Karen Lunde ◽

Iris Söll ◽

...

Keyword(s):

Neuronal Differentiation ◽

Hox Genes ◽

Ectopic Expression ◽

Loss Of Function ◽

Wild Type ◽

Specific Expression ◽

Size And Shape ◽

Regulatory Cascade ◽

Normal Expression ◽

Segmental Identity

Segmentation of the vertebrate hindbrain leads to the formation of a series of rhombomeres with distinct identities. In mouse, Krox20 and kreisler play important roles in specifying distinct rhombomeres and in controlling segmental identity by directly regulating rhombomere-specific expression of Hox genes. We show that spiel ohne grenzen (spg) zebrafish mutants develop rhombomeric territories that are abnormal in both size and shape. Rhombomere boundaries are malpositioned or absent and the segmental pattern of neuronal differentiation is perturbed. Segment-specific expression of hoxa2, hoxb2 and hoxb3 is severely affected during initial stages of hindbrain development in spg mutants and the establishment of krx20 (Krox20 ortholog) and valentino (val; kreisler ortholog) expression is impaired. spg mutants carry loss-of-function mutations in the pou2 gene. pou2 is expressed at high levels in the hindbrain primordium of wild-type embryos prior to activation of krx20 and val. Widespread overexpression of Pou2 can rescue the segmental krx20 and val domains in spg mutants, but does not induce ectopic expression of these genes. This suggests that spg/pou2 acts in a permissive manner and is essential for normal expression of krx20 and val. We propose that spg/pou2 is an essential component of the regulatory cascade controlling hindbrain segmentation and acts before krx20 and val in the establishment of rhombomere precursor territories.

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sisterless A is required for the activation of Sex lethal in the germline

10.1101/2019.12.17.880070 ◽

2019 ◽

Cited By ~ 1

Author(s):

Raghav Goyal ◽

Ellen Baxter ◽

Mark Van Doren

Keyword(s):

Sex Determination ◽

X Chromosome ◽

Germ Cells ◽

Specific Expression ◽

Male Germ Cells ◽

X Chromosomes ◽

Dna Elements ◽

Sex Lethal ◽

Female Specific ◽

Necessary And Sufficient

ABSTRACTIn Drosophila, sex determination in somatic cells has been well-studied and is under the control of the switch gene Sex lethal (Sxl), which is activated in females by the presence of two X chromosomes. Though sex determination is regulated differently in the germline versus the soma, Sxl is also necessary and sufficient for the female identity in germ cells. Loss of Sxl function in the germline results in ovarian germline tumors, a characteristic of male germ cells developing in a female soma. Further, XY (male) germ cells expressing Sxl are able to produce eggs when transplanted into XX (female) somatic gonads, demonstrating that Sxl is also sufficient for female sexual identity in the germline. As in the soma, the presence of two X chromosomes is sufficient to activate Sxl in the germline, but the mechanism for “counting” X chromosomes in the germline is thought to be different from the soma. Here we have explored this mechanism at both cis- and trans-levels. Our data support the model that the Sxl “establishment” promoter (SxlPE) is activated in a female-specific manner in the germline, as in the soma, but that the timing of SxlPE activation, and the DNA elements that regulate SxlPE are different from those in the soma. Nevertheless, we find that the X chromosome-encoded gene sisterless A (sisA), which helps activate Sxl in the soma, is also essential for Sxl activation in the germline. Loss of sisA function leads to loss of Sxl expression in the germline, and to ovarian tumors and germline loss. These defects can be rescued by the expression of Sxl, demonstrating that sisA lies upstream of Sxl in germline sex determination. We conclude that sisA acts as an X chromosome counting element in both the soma and the germline, but that additional factors that ensure robust, female-specific expression of Sxl in the germline remain to be discovered.

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Drosophila melanogaster Y Chromosome Genes Affect Male Sensitivity to Microbial Infections

Insects ◽

10.3390/insects12010030 ◽

2021 ◽

Vol 12 (1) ◽

pp. 30

Author(s):

Gloria Bartolo ◽

Leandra O. Gonzalez ◽

Anastasia Levitin ◽

Mikhail Martchenko Shilman

Keyword(s):

Drosophila Melanogaster ◽

Y Chromosome ◽

Microbial Pathogens ◽

Loss Of Function ◽

Wild Type ◽

Gastrointestinal Infections ◽

Related Function ◽

Microbial Infections ◽

Wild Type Female ◽

Increased Sensitivity

The genders of Drosophila melanogaster vary in their sensitivities to microbial pathogens. While many of the immunity-related genes are located on the X chromosome, the polymorphisms within the Y chromosome were also shown to affect the immunity of flies. In this study, we investigated the necessity of individual genes on the Y chromosome (Y-genes) for male sensitivity to microbes. We identified several Y-genes whose genetic inactivation either increases or decreases the sensitivity of males to gastrointestinal infections with fungal Saccharomyces cerevisiae and bacterial Serratia liquefaciens. Specifically, the loss of function mutations in fly kl-5 and Ppr-Y Y-genes lead to increased and decreased sensitivity of males to fungal challenge, respectively, compared to female sensitivity. In contrast, mutations in Drosophila Pp1-Y1, kl-5, kl-3, Ppr-Y, CCY, and FDY Y-genes lead to increased sensitivity of males to bacterial infection, compared to females. Moreover, while these Y-genes are necessary, the Y chromosome is not sufficient for the sensitivity of males to microbes, since the sensitivity of XXY females to fungal and bacterial challenges was not different from the sensitivity of wild-type female flies, compared to males. This study assigns a new immunity-related function to numerous Y-genes in D.melanogaster.

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A Novel DUF569 Gene Is a Positive Regulator of the Drought Stress Response in Arabidopsis

International Journal of Molecular Sciences ◽

10.3390/ijms22105316 ◽

2021 ◽

Vol 22 (10) ◽

pp. 5316

Author(s):

Rizwana Begum Syed Nabi ◽

Rupesh Tayade ◽

Adil Hussain ◽

Arjun Adhikari ◽

In-Jung Lee ◽

...

Keyword(s):

Abiotic Stress ◽

Drought Stress ◽

Global Environmental Change ◽

Loss Of Function ◽

Wild Type ◽

Positive Regulator ◽

Global Environmental ◽

Acid Accumulation ◽

Domain Of Unknown Function ◽

Rosette Leaf

In the last two decades, global environmental change has increased abiotic stress on plants and severely affected crops. For example, drought stress is a serious abiotic stress that rapidly and substantially alters the morphological, physiological, and molecular responses of plants. In Arabidopsis, several drought-responsive genes have been identified; however, the underlying molecular mechanism of drought tolerance in plants remains largely unclear. Here, we report that the “domain of unknown function” novel gene DUF569 (AT1G69890) positively regulates drought stress in Arabidopsis. The Arabidopsis loss-of-function mutant atduf569 showed significant sensitivity to drought stress, i.e., severe wilting at the rosette-leaf stage after water was withheld for 3 days. Importantly, the mutant plant did not recover after rewatering, unlike wild-type (WT) plants. In addition, atduf569 plants showed significantly lower abscisic acid accumulation under optimal and drought-stress conditions, as well as significantly higher electrolyte leakage when compared with WT Col-0 plants. Spectrophotometric analyses also indicated a significantly lower accumulation of polyphenols, flavonoids, carotenoids, and chlorophylls in atduf569 mutant plants. Overall, our results suggest that novel DUF569 is a positive regulator of the response to drought in Arabidopsis.

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Estrogen Receptor-α Suppresses Liver Carcinogenesis and Establishes Sex-Specific Gene Expression

Cancers ◽

10.3390/cancers13102355 ◽

2021 ◽

Vol 13 (10) ◽

pp. 2355

Author(s):

Mara H. O’Brien ◽

Henry C. Pitot ◽

Sang-Hyuk Chung ◽

Paul F. Lambert ◽

Norman R. Drinkwater ◽

...

Keyword(s):

Gene Expression ◽

Estrogen Receptor ◽

Expression Patterns ◽

Estrogen Receptor Α ◽

Specific Gene ◽

Wild Type ◽

Liver Carcinogenesis ◽

Specific Expression ◽

Liver Gene ◽

Female Specific

Estrogen protects females from hepatocellular carcinoma (HCC). To determine whether this protection is mediated by classic estrogen receptors, we tested HCC susceptibility in estrogen receptor-deficient mice. In contrast to a previous study, we found that diethylnitrosamine induces hepatocarcinogenesis to a significantly greater extent when females lack Esr1, which encodes Estrogen Receptor-α. Relative to wild-type littermates, Esr1 knockout females developed 9-fold more tumors. Deficiency of Esr2, which encodes Estrogen Receptor-β, did not affect liver carcinogenesis in females. Using microarrays and QPCR to examine estrogen receptor effects on hepatic gene expression patterns, we found that germline Esr1 deficiency resulted in the masculinization of gene expression in the female liver. Six of the most dysregulated genes have previously been implicated in HCC. In contrast, Esr1 deletion specifically in hepatocytes of Esr1 conditional null female mice (in which Cre was expressed from the albumin promoter) resulted in the maintenance of female-specific liver gene expression. Wild-type adult females lacking ovarian estrogen due to ovariectomy, which is known to make females susceptible to HCC, also maintained female-specific expression in the liver of females. These studies indicate that Esr1 mediates liver cancer risk, and its control of sex-specific liver gene expression involves cells other than hepatocytes.

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Koala methylomes reveal divergent and conserved DNA methylation signatures of X chromosome regulation

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.2244 ◽

2021 ◽

Vol 288 (1945) ◽

pp. 20202244

Author(s):

Devika Singh ◽

Dan Sun ◽

Andrew G. King ◽

David E. Alquezar-Planas ◽

Rebecca N. Johnson ◽

...

Keyword(s):

Dna Methylation ◽

X Chromosome ◽

Epigenetic Regulation ◽

Specific Expression ◽

X Chromosomes ◽

Phascolarctos Cinereus ◽

Male And Female ◽

Inactive X Chromosome ◽

Promoter Dna ◽

Female Specific

X chromosome inactivation (XCI) mediated by differential DNA methylation between sexes is an iconic example of epigenetic regulation. Although XCI is shared between eutherians and marsupials, the role of DNA methylation in marsupial XCI remains contested. Here, we examine genome-wide signatures of DNA methylation across fives tissues from a male and female koala ( Phascolarctos cinereus ), and present the first whole-genome, multi-tissue marsupial ‘methylome atlas’. Using these novel data, we elucidate divergent versus common features of representative marsupial and eutherian DNA methylation. First, tissue-specific differential DNA methylation in koalas primarily occurs in gene bodies. Second, females show significant global reduction (hypomethylation) of X chromosome DNA methylation compared to males. We show that this pattern is also observed in eutherians. Third, on average, promoter DNA methylation shows little difference between male and female koala X chromosomes, a pattern distinct from that of eutherians. Fourth, the sex-specific DNA methylation landscape upstream of Rsx , the primary lnc RNA associated with marsupial XCI, is consistent with the epigenetic regulation of female-specific (and presumably inactive X chromosome-specific) expression. Finally, we use the prominent female X chromosome hypomethylation and classify 98 previously unplaced scaffolds as X-linked, contributing an additional 14.6 Mb (21.5%) to genomic data annotated as the koala X chromosome. Our work demonstrates evolutionarily divergent pathways leading to functionally conserved patterns of XCI in two deep branches of mammals.

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Interaction of the Stubble-stubbloid locus and the Broad-complex of Drosophila melanogaster.

Genetics ◽

10.1093/genetics/120.2.453 ◽

1988 ◽

Vol 120 (2) ◽

pp. 453-464

Author(s):

A H Beaton ◽

I Kiss ◽

D Fristrom ◽

J W Fristrom

Keyword(s):

Drosophila Melanogaster ◽

X Chromosome ◽

Imaginal Disc ◽

Genetic Locus ◽

Regulatory Gene ◽

Loss Of Function ◽

Wild Type ◽

The Third ◽

Positive Regulator ◽

Broad Complex

Abstract The 2B5 region on the X chromosome of Drosophila melanogaster forms an early ecdysone puff at the end of the third instar. The region is coextensive with a complex genetic locus, the Broad-Complex (BR-C). The BR-C is a regulatory gene that contains two major functional domains, the br domain and the l(1)2Bc domain. BR-C mutants prevent metamorphosis, including morphogenesis of imaginal discs; br mutants prevent elongation and eversion of appendages and l(1)2Bc mutants prevent fusion of the discs. The Stubble-stubbloid (Sb-sbd) locus at 89B9-10 is best known for the effects of its mutants on bristle structure. Mutants of the BR-C and the Sb-sbd locus interact to produce severe malformation of appendages. Viable heteroallelic and homoallelic combinations of Sb-sbd mutants, including loss-of-function mutants, affect the elongation of imaginal disc appendages. Thus, the Sb-sbd+ product is essential for normal appendage elongation. Sb-sbd mutants, however, do not affect eversion or fusion of discs. Correspondingly, only BR-C mutants deficient in br function interact with Sb-sbd mutants. The interaction occurs in deficiency heterozygotes using single, wild-type doses of the BR-C, of the Sb-sbd locus, or of both loci. These last results are formally consistent with the possibility that the BR-C acts as a positive regulator of the Sb-sbd locus. The data do not exclude other possible nonregulatory interactions between the two loci, e.g., interactions between the products of both genes.

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A gene-by-gene mosaic of dosage compensation strategies on the human X chromosome

10.1101/2021.08.09.455676 ◽

2021 ◽

Author(s):

Adrianna K. San Roman ◽

Alexander K. Godfrey ◽

Helen Skaletsky ◽

Daniel W Bellott ◽

Abigail F Groff ◽

...

Keyword(s):

X Chromosome ◽

Dosage Compensation ◽

Sex Chromosome ◽

Loss Of Function ◽

Specific Expression ◽

X Chromosomes ◽

Mediated Effects ◽

Multiple Dimensions ◽

Allele Specific ◽

Health And Disease

Dosage compensation in humans - ensuring the viability and fitness of females, with two X chromosomes, and males, with one - is thought to be achieved chromosome-wide by heterochromatinization of one X chromosome during female development. We reassessed this through quantitative gene-by-gene analyses of expression in individuals with one to four X chromosomes, tolerance for loss-of-function mutations, regulation by miRNAs, allele-specific expression, and the presence of homologous genes on the Y chromosome. We found a mosaic of dosage compensation strategies on the human X chromosome reflecting gene-by-gene differences in multiple dimensions, including sensitivity to under- or over-expression. These insights enrich our understanding of Turner, Klinefelter, and other sex chromosome aneuploidy syndromes, and of sex-chromosome-mediated effects on health and disease in euploid males and females.

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