TAP-like (TAPL; ABCB9) is a half-type ATP-binding cassette (ABC) transporter that localizes in lysosome and putatively conveys peptides from cytosol to lysosome. However, the physiological role of this transporter remains to be elucidated. Comparison of genome databases reveals that TAPL is conserved in various species from a simple model organism, Caenorhabditis elegans, to mammals. C. elegans possesses homologous TAPL genes: haf-4 and haf-9. In this study, we examined the tissue-specific expression of these two genes and analyzed the phenotypes of the loss-of-function mutants for haf-4 and haf-9 to elucidate the in vivo function of these genes. Both HAF-4 and HAF-9 tagged with green fluorescent protein (GFP) were mainly localized on the membrane of nonacidic but lysosome-associated membrane protein homologue (LMP-1)-positive intestinal granules from larval to adult stage. The mutants for haf-4 and haf-9 exhibited granular defects in late larval and young adult intestinal cells, associated with decreased brood size, prolonged defecation cycle, and slow growth. The intestinal granular phenotype was rescued by the overexpression of the GFP-tagged wild-type protein, but not by the ATP-unbound form of HAF-4. These results demonstrate that two ABC transporters, HAF-4 and HAF-9, are related to intestinal granular formation and some other physiological aspects.

Adenosine deaminase-related growth factors (ADGF), also known as CECR1 in vertebrates, are a novel family of growth factors with sequence similarity to classical cellular adenosine deaminase. Although genes for ADGF/CECR1 have been identified in both invertebrates as well as vertebrates, their in vivo functions in vertebrates remain unknown. We isolated cDNA clones for two cerc 1s from Xenopus laevis. Both recombinant Xenopus CECR1s exhibited adenosine deaminase and growth factor activity, and the adenosine deaminase activity was found to be indispensable for growth factor activity. The Xenopus cerc 1s are expressed in the somites, pronephros, eyes, cement gland, neural tube, and neural floor plate of the embryos. Knock-down of these two genes using morpholino oligonucleotides caused a reduction in the body size and abnormalities of the body axis in the Xenopus embryos, accompanied by selective changes in the expression of developmental marker genes. Injection of adenosine, agonists for adenosine/P1 receptors, or adenosine deaminase inhibitor into late gastrula archenteron embryos resulted in developmental defects similar to those caused by morpholino oligonucleotide injection. These results show, for the first time, the involvement of CECR1s via the adenosine/P1 receptors in vertebrate embryogenesis via regulation of extracellular adenosine concentrations.Growth factors play important roles in morphogenesis and organogenesis in various animal species. Of these, the adenosine deaminase-related growth factor (ADGF) 3 family is a novel group of growth factors with sequence similarity to classical adenosine deaminase (ADA) in their carboxyl-terminal regions (1-3). Classical ADA is a cytoplasmic enzyme that catalyzes the deamination of adenosine and 2Ј-deoxyadenosine to inosine and 2Ј-deoxyinosine, respectively (4), and has a wide phylogenetic distribution (5). ADA is involved in purine metabolism and plays an indispensable role in the upkeep of a competent immune system in mammals (6). In contrast, ADGFs are comprised of secretory or transmembrane-type ADGFs (1, 2, 7, 8), with some having growth factor-like activities (3, 9 -14).Insect-derived growth factor (IDGF), the first ADGF to be cloned, is a secretory ADGF purified from the conditioned medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina (flesh fly) (1). IDGF stimulates the growth of NIHSape-4 cells with a specific activity comparable with mammalian growth factors. Site-directed mutagenesis has demonstrated that the ADA activity of IDGF is essential for its growth factor activity (3, 15). So far, ADGF families have been reported in various invertebrates. In Drosophila melanogaster (fruit fly), Male-specific IDGF was identified as a transmembrane-type ADGF and is suggested to participate in spermatogenesis (7). Recently, six ADGFs have been identified in Drosophila, one of which (Adgf-A2) encodes Male-specific IDGF (8, 16). In addition, ADGF families have been identified in other fruit flies, sand flies, sea slugs, tsetse flies, mosquitoes, fu...

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