epidermal-growth-factor and Disorders-of-Sex-Development

During C. elegans development, LIN-12 (Notch) signaling specifies the anchor cell (AC) and ventral uterine precursor cell (VU) fates from two equivalent pre-AC/pre-VU cells in the hermaphrodite gonad. Once specified, the AC induces patterned proliferation of vulva via expression of LIN-3 (EGF) and then invades into the vulval epithelium. Although these cellular processes are essential for the proper organogenesis of vulva and appear to be temporally regulated, the mechanisms that coordinate the processes are not well understood. We computationally identified egl-43 as a gene likely to be expressed in the pre-AC/pre-VU cells and the AC, based on the presence of an enhancer element similar to the one that transcribes lin-3 in the same cells. Genetic epistasis analyses reveal that egl-43 acts downstream of or parallel to lin-12 in AC/VU cell fate specification at an early developmental stage, and functions downstream of fos-1 as well as upstream of zmp-1 and him-4 to regulate AC invasion at a later developmental stage. Characterization of the egl-43 regulatory region suggests that EGL-43 is a direct target of LIN-12 and HLH-2 (E12/47), which is required for the specification of the VU fate during AC/VU specification. EGL-43 also regulates basement membrane breakdown during AC invasion through a FOS-1-responsive regulatory element that drives EGL-43 expression in the AC and VU cells at the later stage. Thus, egl-43 integrates temporally distinct upstream regulatory events and helps program cell fate specification and cell invasion.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cell Movement; Computational Biology; Disorders of Sex Development; Embryonic Induction; Epidermal Growth Factor; Epistasis, Genetic; Gonads; Membrane Proteins; Organogenesis; Receptors, Notch; Stem Cells; Transcription Factors

Caenorhabditis elegans lin-3 encodes a homolog of the epidermal growth factor (EGF) family of growth factors. LIN-3 is the inductive signal for hermaphrodite vulval differentiation, and it is required for animal viability, hermaphrodite fertility, and the specification of anterior cell fates in the male B cell lineage. We describe the cloning of a lin-3 homolog from C. briggsae, sequence comparison of C. elegans lin-3 with C. briggsae lin-3, and the determination of molecular lesions in alleles of C. elegans lin-3, including three new alleles. We also analyzed the severity of phenotypes caused by the new and existing alleles of lin-3. Correlation of mutant phenotypes and their molecular lesions, as well as sequence comparison between two species, reveal that the EGF motif and the N-terminal portion of the cytoplasmic domain are important for the functions of LIN-3 in all tissues, while the C-terminal portion of the cytoplasmic domain is involved in the tissue-specific functions of lin-3. We discuss how the structure of lin-3 contributes to its functions in multiple developmental processes.

Topics: Alleles; Amino Acid Sequence; Animals; Caenorhabditis; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Conserved Sequence; Disorders of Sex Development; Epidermal Growth Factor; Exons; Female; Fertility; Genes, Lethal; Helminth Proteins; Male; Molecular Sequence Data; Phenotype; Polymerase Chain Reaction; Sequence Alignment; Sequence Homology; Suppression, Genetic; Vulva

Activity of LET-23, the C. elegans homolog of the epidermal growth factor receptor, is required in multiple tissues. RAS activation is necessary and sufficient for certain LET-23 functions. We show that an inositol trisphosphate receptor can act as a RAS-independent, tissue-specific positive effector of LET-23. Moreover, an inositol trisphosphate kinase negatively regulates this transduction pathway. Signals transduced by LET-23 control ovulation through changes in spermathecal dilation, possibly dependent upon calcium release regulated by both IP3 and IP4. Our results demonstrate that one mechanism by which receptor tyrosine kinases can evoke tissue-specific responses is through activation of distinct signal transduction cascades in different tissues.

Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Calcium; Calcium Channels; Disorders of Sex Development; Enzyme Activation; Epidermal Growth Factor; ErbB Receptors; Female; Helminth Proteins; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Male; Molecular Sequence Data; Mutagenesis; Ovulation; Protein-Tyrosine Kinases; ras Proteins; Receptors, Cytoplasmic and Nuclear; Sequence Homology, Amino Acid; Signal Transduction; Spermatogenesis

In the nematode worm C. elegans, individuals with mutations in the spe-9 gene produce spermatozoa with wild-type morphology and motility that cannot fertilize oocytes even after contact between gametes. Therefore, disruption of spe-9 function affects either gamete recognition, adhesion, signaling, and/or fusion. The spe-9 gene encodes a sperm transmembrane protein with an extracellular domain that contains ten epidermal growth factor-like repeats. A common feature of proteins that include epidermal growth factor-like motifs is their involvement in extracellular functions such as adhesive and ligand-receptor interactions. Additionally, the overall structure of the predicted SPE-9 protein is similar to that of ligands for the Notch/LIN-12/GLP-1 family of transmembrane receptors. These results suggest that SPE-9 functions in the specialized cell-cell interactions required for fertilization.

Topics: Amino Acid Sequence; Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cloning, Molecular; Disorders of Sex Development; Epidermal Growth Factor; Female; Fertilization; Genes, Helminth; Germ Cells; Male; Membrane Proteins; Molecular Sequence Data; Ovulation; Polymerase Chain Reaction; Recombinant Proteins; Sperm Motility; Sperm-Ovum Interactions; Spermatozoa

The lin-3 gene is necessary for induction of the Caenorhabditis elegans vulva by the anchor cell. It encodes a molecule similar to epidermal growth factor and to transforming growth factor-alpha and acts through the epidermal growth factor receptor homologue let-23. Expression of lin-3 in the anchor cell stimulates vulval induction; lin-3 may encode the vulval inducing signal.

Topics: Amino Acid Sequence; Animals; Animals, Genetically Modified; Base Sequence; Caenorhabditis; Caenorhabditis elegans Proteins; Cloning, Molecular; Disorders of Sex Development; Embryonic Induction; Epidermal Growth Factor; Female; Helminth Proteins; Molecular Sequence Data; Recombinant Fusion Proteins; Stem Cells; Vulva