Spermiogenese in normalen und Y-defizienten M�nnchen von Drosophila melanogaster und D. hydei

Biphasic subcellular localization of the DAZL-related protein boule in Drosophila spermatogenesis

The Drosophila boule gene is expressed exclusively in the male germline and encodes an RNA binding protein closely related to the mammalian fertility factors encoded by the DAZ (Deleted in Azoospermia) and DAZL (DAZ-like) genes. Mutation of boule blocks both meiotic divisions. Differentiation nonetheless continues, resulting in tetraploid spermatids that fail to mature into sperm. We have found that Boule localizes premeiotically to a perinucleolar region and then translocates to the cytoplasm at the onset of meiosis. We show that deletion of the Y chromosome ks-1 fertility locus eliminates Boule nuclear localization, although it does not perturb entry into meiosis. Based on these observations we propose that Boule acts in the cytoplasm to regulate the stability or translation of messenger RNA encoding an essential meiotic factor.

Strukturdifferenzierungen in Y-chromosom von Drosophila hydei: the unique morphology of the Y chromosomal lampbrush loops Threads results from 'coaxial shells' formed by different satellite-specific subregions within megabase-sized transcripts

The results of pulsed-field gel electrophoresis (PFGE) analysis and two-colour transcript fluorescence in situ hybridization (FISH) for the three Threads-specific DNA satellites YLII, YLI and rally are in support of long-range clustering of these sequence families within the subterminal region on the long arm of the Y chromosome of Drosophila hydei. On the basis of the linear arrangement of at least four extended clusters of satellite-specific sequences, the loop morphology of wild-type and several mutant Threads can be explained by assumption of a single Threads-specific transcription unit comprising about 5.1 Mb of repetitive DNA located between the Pseudonucleolus and the Nucleolus organizer. Transcription is unidirectional from the Pseudonucleolus towards the terminally located Nucleolus organizer. Transcripts most likely start in front of or within the 3.2 Mb region of YLII-related sequences, pass through subsequent blocks of 1.2 and 0.3 Mb of YLI- and rally-related sequences, respectively, and cease within the region of a smaller block of YLI-related repeats. The megabase-sized transcripts remain physically linked to the DNA axis and their extended satellite-specific regions form coaxial clouds or shells around the central DNA axis. In this way each cluster of earlier-transcribed sequences generates a cloud or shell on top of the later-transcribed ones. According to this model of 'satellite-specific coaxial shells' the tube-like morphology and other peculiarities of the Y chromosomal lampbrush loops Threads can be explained as a result of satellite-specific RNA superstructures and/or formation of extended ribonucleoprotein (RNP) complexes between clusters of satellite-specific transcripts and specific proteins. On the basis of this model the specific morphology of several Threads mutants can be interpreted as the result of large interstitial or terminal deletions that alter the total length of the Threads-specific transcription unit without exerting other major effects on principal features of the transcription process along the Threads.

Genetic analysis of variation in the number of primary spermatocytes per cyst in Drosophila virilis

Two experiments were performed with the aim of clarifying the genetic basis of variation in the number of primary spermatocytes per cyst in the B12 strain of Drosophila virilis and identifying the chromosome responsible for the variation. First, crosses between B12, showing a mean cell number of 11.81, and strain TK with a mean of 7.91, were performed. From the results obtained, it was considered that there were two factors, i.e., a recessive gene and certain modifiers, which shifted the cell number toward a higher value in B12. Second, chromosomal analysis with a marker strain and the B12 strain revealed that the third chromosome of B12 was responsible for the major effect of changing the primary spermatocyte number, although this chromosome did not exert a sufficient effect alone, and furthermore that at least one of the modifiers located on the second chromosome.

Involvement of Y chromosomal loci in the synthesis of Drosophila hydei sperm proteins

A comparative study of the protein patterns in testes of wild-type and X/O flies of Drosophila hydei revealed quantitative differences in at least three major protein fractions. One protein component of a Mr 155,000 fraction and a protein of Mr 35,000 are completely absent in X/O testes. The amount of protein in a Mr 55,000 fraction is considerably reduced. The tubulins, which are part of this fraction, are also reduced in amount. All three proteins were found as constituents of sperm tails. Studies of Y chromosomal mutants revealed that the presence of at least two of these proteins depends on the activity of loci O, P, and Q of the Y chromosome. However, preliminary evidence indicates an autosomal location of the genes of these sperm proteins. This suggests a regulatory role of Y chromosomal genes in the production of some major sperm proteins.

Analysis of nuclear proteins in primary spermatocytes of Drosophila hydei: The correlation of nuclear proteins with the function of the Y chromosomal loops

The protein content of spermatocyte nuclei from X/Y males and mutants of D. hydei which lack different Y chromosomal loop forming sites, was compared with that of X/0 males in 14C/3H double labelling experiments. Proteins of 45,000, 52,000, 54,000, 66,000, 80,000, 84,000 and 170,000 Dalton are found to be enriched in nuclei containing two or more active Y chromosomal loop forming sites. These proteins are also present in the nuclei of X0 males. In the complete absence of the Y-chromosomal loops proteins of 35,000, 46,000, 58,000 and 110,000 Dalton become enriched in the spermatocyte nuclei. - Analysis of the nuclear RNP of spermatocytes led to the isolation of an hnRNP-containing fraction with an S-value of greater than 900S (RNP-PP), - In the RNP-PP of XY males labelled protein material associated with hnRNA is enriched by a factor of approximately 3 in respect to the X0 genotype. The nuclear RNP has a heterogenous buoyant density in CsCl of rho = 1.33 to 1.43 g/cm3. RNase T1 treatment of the crude nuclear RNP from XY males prior to sucrose gradient analysis shows that the 66,000 Dalton protein which is also strongly enriched in the nuclei in the presence of active Y chromosomal loop forming sites, is the main protein associated with protected RNA-sequences of 80-120- 300 nucleotides in length. Competitive nitrocellulose filter binding assays reveal that the 66,000 Dalton protein predominantly forms in 2 M NaCl stable RNA/protein complexes with the poly A+hnRNA of the RNP-PP. Those RNP complexes have a buoyant density of rho = 1.43 g/cm3 in CsCl. The results are discussed in relation to the nuclear structure and the function of the Y chromosomal loops during spermatogenesis in Drosophila hydei.

Analysis of spermatogenesis in Drosophila melanogaster bearing deletions for Y-chromosome fertility genes

The effects of spermatogenesis of a series of continguous non-overlapping Y-chromosome deficiencies were examined using both the light and electron microscope. The deficiencies were constructed by combining elements of different X-Y translocations; they subdivide the Y into seven segments, six of which are required for male fertility (four in the long arm and two in the short arm). Spermatogenesis was examined from the primary spermatocyte through to the formation of mature sperm and the earliest departures from normal development identified. Two deficiencies result in the absence of the same structure from the axoneme of the sperm tail--the dynein-containing outer arm extending from the A subtubule of the peripheral doublet; they also result in the absence from primary spermatocyte nuclei of aggregates of tubuli in one case and reticular material in the other. A third deficiency causes the appearance in the primary spermatocyte of the crystals characteristic of X0 males and the irregular distribution during meiosis of nuclear and cytoplasmic elements to the spermatids. The fourth deficiency results in the misalignment of the developing axoneme with the mitochondrial derivatives and is first detectable in the onion nebenkern stage of the spermatid. Finally for two deficiencies the first abnormalities detected were during later stages and comprise a syndrome found in most of the steriles. We attribute this phenotype to the indirect effects of earlier lesions.

Ultrastructural studies on spermatogenesis in a sex-ratio-mutant strain of Drosophila simulans

The aberrant sex-ratio mutation in D. simulans used for this study is a temperature-sensitive autosomal recessive. Homozygous males raised at 16 degrees C produce about 2% of F1, but those raised at 26 degrees C, have a normal sex ratio. Ultrastructural studies of spermatogenesis have revealed many anomalies in the germ cells of flies raised at 16 degrees C, but the same flies raised at 26 degrees C had few anomalies. The earliest spermatogenic stage with noticeable abnormalities was the primary spermatocyte. In later stages there were pronounced abnormalities in nucleoli, chromatin condensation, nuclear shape, Golgi complex, acrosome, and microtubules. There is asynchronous differentiation of spermatids within a bundle. Some of the abnormalities encountered are disorganization or loss of microtubules of the axoneme, degenerating nebenkern derivatives, and increased numbers of lysosomes, multilamellate bodies, and multivesicular bodies. At the lower temperature, more than half of the sperm within the same bundle were found in different stages of degeneration. Genetic analysis suggests that the sex-ratio gene causes abnormalities and degeneration of most of the Y-bearing sperm. However, counts of abnormal sperm at the ultrastructural level indicate that some X-bearing sperm must also undergo degeneration. These observations show that the sex-ratio gene is of variable penetrance at different temperatures in the primary spermatocyte and of differential penetrance in X- and Y-bearing sperm.