Abnormal arterial-venous fusions and fate specification in mouse embryos lacking blood flow.

The functions of blood flow in the morphogenesis of mammalian arteries and veins are not well understood. We examined the development of the dorsal aorta (DA) and the cardinal vein (CV) in Ncx1 mutants, which lack blood flow due to a deficiency in a sodium calcium ion exchanger expressed specifically in the heart. The mutant DA and CV were abnormally connected.

Neural crest defects in ephrin-B2 mutant mice are non-autonomous and originate from defects in the vasculature.

Ephrin-B2, a member of the Eph/ephrin family of cell signaling molecules, has been implicated in the guidance of cranial and trunk neural crest cells (NCC) and development of the branchial arches(BA), but detailed examination in mice has been hindered by embryonic lethality of Efnb2 null loss of function due to a requirement in angiogenic remodeling. To elucidate the developmental roles for Efnb2, we generated a conditional rescue knock-in allele that allows rescue of ephrin-B2 specifically in the vascular endothelium (VE), but is otherwise ephrin-B2 deficient. Restoration of ephrin-B2 expression specifically to the VE completely circumvents angiogenic phenotypes, indicating that the requirement of ephrin-B2 in angiogenesis is limited to the VE.

Large-scale mapping of transposable element insertion sites using digital encoding of sample identity.

Determining the genomic locations of transposable elements is a common experimental goal. When mapping large collections of transposon insertions, individualized amplification and sequencing is both time consuming and costly. We describe an approach in which large numbers of insertion lines can be simultaneously mapped in a single DNA sequencing reaction by using digital error-correcting codes to encode line identity in a unique set of barcoded pools.

Apical-basal polarity proteins are required cell-type specifically to direct photoreceptor morphogenesis.

Insect photoreceptor function is dependent on precise placement of the rhabdomeres, elaborated apical domains specialized for capturing light, within each facet of a compound eye. In Diptera, an asymmetric arrangement of rhabdomeres, combined with a particular pattern of axonal connections, enhances light sensitivity through the principle of neural superposition. To achieve the necessary retinal geometry, different photoreceptors (R cells) have distinct shapes.

The cytoskeletal regulator Genghis khan is required for columnar target specificity in the Drosophila visual system.

A defining characteristic of neuronal cell type is the growth of axons and dendrites into specific layers and columns of the brain. Although differences in cell surface receptors and adhesion molecules are known to cause differences in synaptic specificity, differences in downstream signaling mechanisms that determine cell type-appropriate targeting patterns are unknown. Using a forward genetic screen in Drosophila, we identify the GTPase effector Genghis khan (Gek) as playing a crucial role in the ability of a subset of photoreceptor (R cell) axons to innervate appropriate target columns.

Complex interactions amongst N-cadherin, DLAR, and Liprin-alpha regulate Drosophila photoreceptor axon targeting.

The formation of stable adhesive contacts between pre- and post-synaptic neurons represents the initial step in synapse assembly. The cell adhesion molecule N-cadherin, the receptor tyrosine phosphatase DLAR, and the scaffolding molecule Liprin-alpha play critical, evolutionarily conserved roles in this process. However, how these proteins signal to the growth cone and are themselves regulated remains poorly understood.

Germ-line specific variants of components of the mitochondrial outer membrane import machinery in Drosophila.

A search of the Drosophila genome for genes encoding components of the mitochondrial translocase of outer membrane (TOM) complex revealed duplication of genes encoding homologues of Tom20 and Tom40. Tom20 and Tom40 were represented by two differentially expressed homologues in the Drosophila genome. While dtom20 and dtom40 appeared to be expressed ubiquitously, the second variants, called tomboy20 and tomboy40, were expressed only in the male germ-line.

Differential expression of the Drosophila mitofusin genes fuzzy onions (fzo) and dmfn.

Mitofusins comprise a family of evolutionarily conserved, nuclear encoded mitochondrial guanosine triphoshatases that control mitochondrial fusion and morphology. The fuzzy onions (fzo) and Drosophila mitofusin (dmfn) genes, which encode the only Mitofusin homologs in Drosophila are differentially expressed during development. Dmfn-mRNA was widely expressed during embryogenesis accumulating in the mesoderm and endoderm during gut development, during oogenesis with transcripts maternally deposited into the early embryo and in the male germ line, where dmfn-mRNA was expressed in spermatogonia, spermatocytes and early spermatids.