Sex Differentiation: The process in developing sex- or gender-specific tissue, organ, or function after SEX DETERMINATION PROCESSES have set the sex of the GONADS. Major areas of sex differentiation occur in the reproductive tract (GENITALIA) and the brain.Gonads: The gamete-producing glands, OVARY or TESTIS.Sex Determination Processes: The mechanisms by which the SEX of an individual's GONADS are fixed.Cell Differentiation: Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs.Aromatase: An enzyme that catalyzes the desaturation (aromatization) of the ring A of C19 androgens and converts them to C18 estrogens. In this process, the 19-methyl is removed. This enzyme is membrane-bound, located in the endoplasmic reticulum of estrogen-producing cells of ovaries, placenta, testes, adipose, and brain tissues. Aromatase is encoded by the CYP19 gene, and functions in complex with NADPH-FERRIHEMOPROTEIN REDUCTASE in the cytochrome P-450 system.Disorders of Sex Development: In gonochoristic organisms, congenital conditions in which development of chromosomal, gonadal, or anatomical sex is atypical. Effects from exposure to abnormal levels of GONADAL HORMONES in the maternal environment, or disruption of the function of those hormones by ENDOCRINE DISRUPTORS are included.Testis: The male gonad containing two functional parts: the SEMINIFEROUS TUBULES for the production and transport of male germ cells (SPERMATOGENESIS) and the interstitial compartment containing LEYDIG CELLS that produce ANDROGENS.Ovary: The reproductive organ (GONADS) in female animals. In vertebrates, the ovary contains two functional parts: the OVARIAN FOLLICLE for the production of female germ cells (OOGENESIS); and the endocrine cells (GRANULOSA CELLS; THECA CELLS; and LUTEAL CELLS) for the production of ESTROGENS and PROGESTERONE.Hermaphroditic Organisms: Animals and plants which have, as their normal mode of reproduction, both male and female sex organs in the same individual.Androstatrienes: Derivatives of the steroid androstane having three double bonds at any site in any of the rings.Testicular Hormones: Hormones produced in the testis.Fish Proteins: Proteins obtained from species of fish (FISHES).Oryzias: The only genus in the family Oryziinae, order BELONIFORMES. Oryzias are egg-layers; other fish of the same order are livebearers. Oryzias are used extensively in testing carcinogens.Sex Characteristics: Those characteristics that distinguish one SEX from the other. The primary sex characteristics are the OVARIES and TESTES and their related hormones. Secondary sex characteristics are those which are masculine or feminine but not directly related to reproduction.Mesonephros: One of a pair of excretory organs (mesonephroi) which grows caudally to the first pair (PRONEPHROI) during development. Mesonephroi are the permanent kidneys in adult amphibians and fish. In higher vertebrates, proneprhoi and most of mesonephroi degenerate with the appearance of metanephroi. The remaining ducts become WOLFFIAN DUCTS.Germ Cells: The reproductive cells in multicellular organisms at various stages during GAMETOGENESIS.SOX9 Transcription Factor: A SOXE transcription factor that plays a critical role in regulating CHONDROGENESIS; OSTEOGENESIS; and male sex determination. Loss of function of the SOX9 transcription factor due to genetic mutations is a cause of CAMPOMELIC DYSPLASIA.Oogonia: Euploid female germ cells of an early stage of OOGENESIS, derived from primordial germ cells during ovarian differentiation. Oogonia undergo MEIOSIS and give rise to haploid OOCYTESGene Expression Regulation, Developmental: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action during the developmental stages of an organism.Anti-Mullerian Hormone: A glycoprotein that causes regression of MULLERIAN DUCTS. It is produced by SERTOLI CELLS of the TESTES. In the absence of this hormone, the Mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent Mullerian duct, a form of MALE PSEUDOHERMAPHRODITISM.Sex-Determining Region Y Protein: A transcription factor that plays an essential role in the development of the TESTES. It is encoded by a gene on the Y chromosome and contains a specific HMG-BOX DOMAIN that is found within members of the SOX family of transcription factors.Genitalia: The external and internal organs related to reproduction.Steroidogenic Factor 1: A transcription factor and member of the nuclear receptor family NR5 that is expressed throughout the adrenal and reproductive axes during development. It plays an important role in sexual differentiation, formation of primary steroidogenic tissues, and their functions in post-natal and adult life. It regulates the expression of key steroidogenic enzymes.Genes, sry: The primary testis-determining gene in mammalians, located on the Y CHROMOSOME. It codes for a high mobility group box transcription factor (TRANSCRIPTION FACTORS) which initiates the development of the TESTES from the embryonic GONADS.Gonadal Dysgenesis: A number of syndromes with defective gonadal developments such as streak GONADS and dysgenetic testes or ovaries. The spectrum of gonadal and sexual abnormalities is reflected in their varied sex chromosome (SEX CHROMOSOMES) constitution as shown by the karyotypes of 45,X monosomy (TURNER SYNDROME); 46,XX (GONADAL DYSGENESIS, 46XX); 46,XY (GONADAL DYSGENESIS, 46,XY); and sex chromosome MOSAICISM; (GONADAL DYSGENESIS, MIXED). Their phenotypes range from female, through ambiguous, to male. This concept includes gonadal agenesis.46, XY Disorders of Sex Development: Congenital conditions in individuals with a male karyotype, in which the development of the gonadal or anatomical sex is atypical.DAX-1 Orphan Nuclear Receptor: An orphan nuclear receptor that is implicated in regulation of steroidogenic pathways. It is unlike most orphan nuclear receptors in that it appears to lack an essential DNA-binding domain and instead acts as a transcriptional co-repressor. Mutations in the gene Dax-1 cause congenital adrenal hypoplasia.Fushi Tarazu Transcription Factors: Fushi tarazu transcription factors were originally identified in DROSOPHILA. They are found throughout ARTHROPODS and play important roles in segmentation and CENTRAL NERVOUS SYSTEM development.Sex Chromosomes: The homologous chromosomes that are dissimilar in the heterogametic sex. There are the X CHROMOSOME, the Y CHROMOSOME, and the W, Z chromosomes (in animals in which the female is the heterogametic sex (the silkworm moth Bombyx mori, for example)). In such cases the W chromosome is the female-determining and the male is ZZ. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Sertoli Cells: Supporting cells projecting inward from the basement membrane of SEMINIFEROUS TUBULES. They surround and nourish the developing male germ cells and secrete ANDROGEN-BINDING PROTEIN and hormones such as ANTI-MULLERIAN HORMONE. The tight junctions of Sertoli cells with the SPERMATOGONIA and SPERMATOCYTES provide a BLOOD-TESTIS BARRIER.Transcription Factors: Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process.Hypospadias: A birth defect due to malformation of the URETHRA in which the urethral opening is below its normal location. In the male, the malformed urethra generally opens on the ventral surface of the PENIS or on the PERINEUM. In the female, the malformed urethral opening is in the VAGINA.Androgen-Insensitivity Syndrome: A disorder of sexual development transmitted as an X-linked recessive trait. These patients have a karyotype of 46,XY with end-organ resistance to androgen due to mutations in the androgen receptor (RECEPTORS, ANDROGEN) gene. Severity of the defect in receptor quantity or quality correlates with their phenotypes. In these genetic males, the phenotypic spectrum ranges from those with normal female external genitalia, through those with genital ambiguity as in Reifenstein Syndrome, to that of a normal male with INFERTILITY.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Reverse Transcriptase Polymerase Chain Reaction: A variation of the PCR technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard PCR protocols.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Y Chromosome: The male sex chromosome, being the differential sex chromosome carried by half the male gametes and none of the female gametes in humans and in some other male-heterogametic species in which the homologue of the X chromosome has been retained.Sex Factors: Maleness or femaleness as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or effect of a circumstance. It is used with human or animal concepts but should be differentiated from SEX CHARACTERISTICS, anatomical or physiological manifestations of sex, and from SEX DISTRIBUTION, the number of males and females in given circumstances.Gene Expression Profiling: The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.Zebrafish: An exotic species of the family CYPRINIDAE, originally from Asia, that has been introduced in North America. They are used in embryological studies and to study the effects of certain chemicals on development.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.Fishes: A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.Larva: Wormlike or grublike stage, following the egg in the life cycle of insects, worms, and other metamorphosing animals.Stem Cells: Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Embryonic Stem Cells: Cells derived from the BLASTOCYST INNER CELL MASS which forms before implantation in the uterine wall. They retain the ability to divide, proliferate and provide progenitor cells that can differentiate into specialized cells.Cell Lineage: The developmental history of specific differentiated cell types as traced back to the original STEM CELLS in the embryo.Sex: The totality of characteristics of reproductive structure, functions, PHENOTYPE, and GENOTYPE, differentiating the MALE from the FEMALE organism.Cell Division: The fission of a CELL. It includes CYTOKINESIS, when the CYTOPLASM of a cell is divided, and CELL NUCLEUS DIVISION.Estradiol: The 17-beta-isomer of estradiol, an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position. Estradiol-17-beta is the most potent form of mammalian estrogenic steroids.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.Cell Proliferation: All of the processes involved in increasing CELL NUMBER including CELL DIVISION.Tretinoin: An important regulator of GENE EXPRESSION during growth and development, and in NEOPLASMS. Tretinoin, also known as retinoic acid and derived from maternal VITAMIN A, is essential for normal GROWTH; and EMBRYONIC DEVELOPMENT. An excess of tretinoin can be teratogenic. It is used in the treatment of PSORIASIS; ACNE VULGARIS; and several other SKIN DISEASES. It has also been approved for use in promyelocytic leukemia (LEUKEMIA, PROMYELOCYTIC, ACUTE).Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Osteogenesis: The process of bone formation. Histogenesis of bone including ossification.Osteoblasts: Bone-forming cells which secrete an EXTRACELLULAR MATRIX. HYDROXYAPATITE crystals are then deposited into the matrix to form bone.Mice, Inbred C57BLHomeodomain Proteins: Proteins encoded by homeobox genes (GENES, HOMEOBOX) that exhibit structural similarity to certain prokaryotic and eukaryotic DNA-binding proteins. Homeodomain proteins are involved in the control of gene expression during morphogenesis and development (GENE EXPRESSION REGULATION, DEVELOPMENTAL).Antigens, Differentiation: Antigens expressed primarily on the membranes of living cells during sequential stages of maturation and differentiation. As immunologic markers they have high organ and tissue specificity and are useful as probes in studies of normal cell development as well as neoplastic transformation.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Mesenchymal Stromal Cells: Bone-marrow-derived, non-hematopoietic cells that support HEMATOPOETIC STEM CELLS. They have also been isolated from other organs and tissues such as UMBILICAL CORD BLOOD, umbilical vein subendothelium, and WHARTON JELLY. These cells are considered to be a source of multipotent stem cells because they include subpopulations of mesenchymal stem cells.Adipogenesis: The differentiation of pre-adipocytes into mature ADIPOCYTES.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Myoblasts: Embryonic (precursor) cells of the myogenic lineage that develop from the MESODERM. They undergo proliferation, migrate to their various sites, and then differentiate into the appropriate form of myocytes (MYOCYTES, SKELETAL; MYOCYTES, CARDIAC; MYOCYTES, SMOOTH MUSCLE).Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Cell Culture Techniques: Methods for maintaining or growing CELLS in vitro.Muscle Development: Developmental events leading to the formation of adult muscular system, which includes differentiation of the various types of muscle cell precursors, migration of myoblasts, activation of myogenesis and development of muscle anchorage.Hematopoietic Stem Cells: Progenitor cells from which all blood cells derive.Adipocytes: Cells in the body that store FATS, usually in the form of TRIGLYCERIDES. WHITE ADIPOCYTES are the predominant type and found mostly in the abdominal cavity and subcutaneous tissue. BROWN ADIPOCYTES are thermogenic cells that can be found in newborns of some species and hibernating mammals.Bone Marrow Cells: Cells contained in the bone marrow including fat cells (see ADIPOCYTES); STROMAL CELLS; MEGAKARYOCYTES; and the immediate precursors of most blood cells.In Situ Hybridization: A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes.Keratinocytes: Epidermal cells which synthesize keratin and undergo characteristic changes as they move upward from the basal layers of the epidermis to the cornified (horny) layer of the skin. Successive stages of differentiation of the keratinocytes forming the epidermal layers are basal cell, spinous or prickle cell, and the granular cell.Unsafe Sex: Sexual behaviors which are high-risk for contracting SEXUALLY TRANSMITTED DISEASES or for producing PREGNANCY.Embryo, Mammalian: The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.Trans-Activators: Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins.Tumor Cells, Cultured: Cells grown in vitro from neoplastic tissue. If they can be established as a TUMOR CELL LINE, they can be propagated in cell culture indefinitely.Basic Helix-Loop-Helix Transcription Factors: A family of DNA-binding transcription factors that contain a basic HELIX-LOOP-HELIX MOTIF.Promoter Regions, Genetic: DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.Dimethyl Sulfoxide: A highly polar organic liquid, that is used widely as a chemical solvent. Because of its ability to penetrate biological membranes, it is used as a vehicle for topical application of pharmaceuticals. It is also used to protect tissue during CRYOPRESERVATION. Dimethyl sulfoxide shows a range of pharmacological activity including analgesia and anti-inflammation.Flow Cytometry: Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.