Membrane flow during nematode spermiogenesis.

Abstract

Two distinct types of surface membrane rearrangement occur during the differentiation of Caenorhabditis elegans spermatids into amoeboid spermatozoa. The first, detected by the behavior of latex beads attached to the surface, is a nondirected, intermittent movement of discrete portions of the membrane . This movement starts when spermatids are stimulated to differentiate and stops when a pseudopod is formed . The second type of movement is a directed, continual flow of membrane components from the tip of the pseudopod to its base . Both membrane glycoproteins and fluorescent phospholipids inserted in the membrane flow backward at the same rate,^-4 Lm/min, although their lateral diffusion coefficients in the membrane differ by at least a factor of 5 . These observations suggest that pseudopodial membrane movement is due to bulk flow of membrane components away from the tip of the pseudopod.Membrane components move over the surfaces of many cell types, particularly motile cells . These movements can occur without net membrane rearrangement as typified by the bidirectional movement of surface-attached latex beads on the flagellar membrane of Chlamydomonas (6). More often, membrane movement is unidirectional resulting in net rearrangement of membrane components. This is the case for capping of externally cross-linked antigens, lectin receptors and insulin receptors on lymphocytes (23, 24), and for "tipping" of sexual agglutinins on adherent Chlamydomonas gametes (11) . Amoeboid cells exhibit yet another form of directed membrane movement in which surface markers are transported centripetally from the leading edge toward the cell body (1) . Neither the mechanisms underlying these movements nor their physiological significance are understood.In this study, we have examined membrane movements during differentiation of the amoeboid spermatozoa of the nematode, Caenorhabditis elegans. The terminal step in differentiation of these cells is the rapid conversion of spherical, sessile spermatids into polarized, motile spermatozoa. This event can be induced in vitro with the monovalent ion ionophore, monensin (18). It requires extensive cytoplasmic rearrangements : laminar membranes underlying plasma membrane in spermatids accumulate at the base of the pseudopod; membranous organelles (MO) fuse with the plasma membrane; and a pseudopod, which is devoid of organelles but filled with amorphous cytoplasm, extends 3-4 lam from the hemispherical cell body (18,29) .Here, we demonstrate that extensive surface membrane rearrangement accompanies this cytoplasmic differentiation .

Reduction in ovulation or male sex phenotype increases long-term anoxia survival in adaf-16-independent manner inCaenorhabditis elegans

“…fer- 15(hc15ts) fer-15 activity is required for spermatogenesis. The mutant hermaphrodite has spermatids that fail to activate into mature spermatozoa (57).…”

“…The fog-2(q71) female rarely lays unfertilized oocytes, whereas the spe-9(hc52ts) and fer-15(hc15ts) animals do lay unfertilized oocytes at a significant rate; therefore, it is possible that an increase in oocyte maturation and ovulation phenotype will suppress the long-term anoxia survival phenotype observed in the fog-2(q71) female (35,57). To test this, we analyzed mated fog-2(q71) animals and determined that mating the fog-2(q71) female with males that have functional sperm [fog-2(q71) or wild-type males], before anoxia exposure, suppressed the long-term anoxia survival phenotype (Table 4 and data not shown, respectively).…”

Isolation and characterization of a sperm-specific gene family in the nematode Caenorhabditis elegans.

“…The pseudopodial movement of mature sperm involves the addition of membrane components at the growing tip and subsequent flow from the tip back toward the cell body (43,44). One of the possible roles of the MSP is to aid in the transport of new membrane components (phospholipids) from the cell body to the growing tip of the pseudopod (58 Methylation has been hypothesized to play an important role in gene regulation (41).…”

Variation ofBurkholderia cenocepaciavirulence potential during cystic fibrosis chronic lung infection

“…Equal volumes of these cell suspensions and 1.5% (w/v) low-melting-point agarose (FMC Bioproducts, Rockland, Me., USA) were mixed, and 100 ml aliquots were dispensed into insert molds to solidify. Gel plugs were treated with a lysis solution (6 mM Tris-HCl, 1 M NaCl, 0.01 M EDTA, 0.5% Brij-58, 0.2% deoxycholate and 0.5% N-lauroylsarcosine, pH 7.6) overnight at 37 C. The purification of DNA in gel plugs was performed by the standard proteinase K method (0.5 M EDTA, 1% (w/ v) N-lauroylsarcosine, 1 mg/ml proteinase K) at 50 C for 24 h, followed by an additional period of 24 h in the same fresh solution without proteinase K at 50 C. Gel plugs were finally washed several times with TE buffer (10 mM Tris-HCl and 1 mM EDTA, pH 7.6) at 37 C, and then stored at 4 C in TE buffer. These gel plugs were used directly for chromosome separation by PFGE or after digestion with SpeI to separate the generated macrofragments by PFGE.…”