Worm Breeder's Gazette 13(3): 51 (June 1, 1994)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.


Benjamin Podbilewicz

MRC Laboratory of Molecular Biology, Cambridge, UK

Disintegrins are a family of peptides found in some snake venoms that interfere with the binding of integrin receptors to their ligands. Disintegrins are secreted proteins that bind to integrins and inhibit platelet aggregation causing bleeding. Recently a new family of membrane proteins containing disintegrin domains has been identified in mammals.(1), (2) Disintegrin containing proteins probably function in cell-cell and cell-matrix interactions in sperm(2), epididymis(3), monocytes(1), lung(4), and muscle.(4) A secreted disintegrin-containing gene has been implicated as a candidate breast cancer tumour suppressor gene.(5) Snake venom disintegrins are the mature forms of precursors that contain metalloprotease domains. The mammalian genes encode multidomain membrane proteins containing: a) proprotein domain containing signal sequence and precursor region; b) metalloprotease domain; c) disintegrin domain; d) cysteine-rich domain; e) epidermal growth factor repeat; f) transmembrane domain; and g) cytoplasmic domain. Snake venom haemorrhagic proteins do not have the last three domains.(1)

PH30 ,a sperm heterodimeric protein of the disintegrin family is involved in sperm-egg fusion(2). I hypothesized that homologues of PH30 in the nematode could have a role not only in fertilization but also in somatic fusions.(6) A cDNA ( cm14 h10 ,RIII) partially sequenced by the Cambridge/St. Louis sequencing group, encodes a worm protein containing sequences similar to snake and mammalian disintegrins.(7) I sequenced cm14 h10 and used it to screen S. Kim's cDNA library. A 3.7 kb clone encodes a predicted protein containing the multidomain organization of the mammalian members of the disintegrin family. Northern blot analysis on adults and mixed stage populations revealed a major mRNA of 3.6 kb and other species of 2.5 and 2.0 kb. Polyclonal antibodies against guinea pig sperm disintegrin proteins(8) recognize peptides of the expected molecular weights on western blots of C. elegans lysates. Affinity purified antipeptide antibodies against the encoded worm homologue identify a putative precursor of >110 kD and candidate processed peptides of ~80, 50 and 30 kD. Using two different polyclonal sera against different epitopes I have found expression by immunofluorescence in sheath cells of the amphids and cephalic sensilla. Low stringency Southern blot analysis detects a single gene hybridizing with cm14 h10 .To search for other disintegrins in the worm I am using nested PCR. The expression pattern suggests a role in sensilla development perhaps involving cell-cell (neuron/sheath or socket/sheath) and cell-matrix interactions. To elucidate the function of disintegrin-containing genes in the worm I will try to isolate mutations in the snake venom disintegrin domain and in the other domains.

Literature Cited:

(1) Wolfsberg, T.G., et al. Proc. Natl. Acad. Sci. USA 90,10783-10787 (1993).

(2) Blobel, C.P., et al. Nature 356, 248-252 (1992).

(3) Perry, A.C.F., Jones, R., Barker, P.J. & Hall, L. Biochem. J. 286, 671-675 (1992).

(4) Weskamp, G. & Blobel, C.P. Proc. Natl. Acad. Sci. USA 91, 2748-2751 (1994).

(5) Emi, M., et al. Nature Genetics 5,151-157 (1993).

(6) Podbilewicz, B. & White, J.G. Dev. Biol. 161, 408-424 (1994).

(7) Podbilewicz, B. To fuse or not to fuse: A developmental question 18 (Madison, 1993). (8) Blobel, C.P., Myles, D.G., Primakoff, P. & White, J.M. J. Cell Biol. 111, 69-78 (1990).