The Significance of the Sex Chromatin*

Barr, Murray L.

doi:10.1016/s0074-7696(08)60564-1

Cited by 30 publications

(2 citation statements)

References 198 publications

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“…However, the simplest interpretation is that the differential X versus autosome expression reflects early cessation of X chromosome transcription in spermatogenesis. This interpretation is consistent with the observation that early X chromosome inactivation occurs in spermatogenesis in mammals [Monesi, 1965;Richler et al, 19891 and in the grasshopper [Nur, 1978, 19811. Previous data as to whether this occurs in Drosophila have been ambiguous [Lifschytz and Lindsley, 1972;Wu and Davis, 19931. Cytological studies of Drosophila spermatogenesis have failed to provide evidence for early inactivation of the X chromosome through a mechanism of early condensation [Kremer et al, 19861. However, it should be noted that in both mammals and grasshoppers, X chromosome inactivation via X chromosome condensation is also used as a means of dosage compensation in somatic cells [Barr, 1966;Rao and Padmaja, 19921. Mammals and grasshoppers may show the result of adaptation of a mechanism of X chromosome condensation to two tasks. Dosage compensation in Drosophila is not accomplished by X chromosome inactivation.…”

Section: Early Cessation Of X-chromosome Expression In the Drosophilumentioning

confidence: 99%

Regulation of β‐tubulin function and expression in Drosophila spermatogenesis

et al. 1995

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In this study we examined two aspects of beta-tubulin function in Drosophila spermatogenesis: 1) beta-tubulin structural requirements for assembly of different categories of microtubules and 2) regulatory requirements for production of the correct tubulin protein level. In normal Drosophila spermatogenesis, the testis-specific beta 2-tubulin isoform supports multiple microtubule functions. Our previous work showed that another Drosophila isoform, beta 3, cannot support spermatogenesis, whereas a carboxyl-truncated form of beta 2, beta 2 delta C, can at least to some extent provide all of beta 2's normal functions, save one: beta 2 delta C cannot support organization of axonemal microtubules into the supramolecular architecture of the axoneme. Here, to test whether beta 2 carboxyl sequences can rescue the functional failure of the beta 3 isoform in spermatogenesis, we constructed a gene encoding a chimeric protein, beta 3 beta 2C, in which beta 3 sequences in the carboxyl region are replaced with those of beta 2. Unlike either beta 3 or beta 2 delta C, beta 3 beta 2C can provide partial function for both assembly of axonemal microtubules and their organization into the supramolecular architecture of the axoneme. In particular, the beta 2 carboxyl sequences mediate morphogenesis of the axoneme doublet tubule complex, including accessory microtubule assembly and attachment of spokes and linkers. However, our data also reveal aspects of beta 2-specific function that require structural features other than the primary sequence of the isotype-defining variable regions, the C terminus and the internal variable region. Tests of fecundity in males that coexpress beta 2 and the chimeric beta 3 beta 2C protein showed that in Drosophila there are differential requirements for sperm motility in the male and in the female reproductive tract. Since some aspects of microtubule function in spermatogenesis are sensitive to the tubulin pool size, we examined the mechanisms for control of tubulin protein levels in the male germ cells. We found that both beta 2-tubulin mRNA accumulation and protein synthesis are dependent on gene dose, and that the level of expression is regulated by 3' noncoding sequences in the beta 2 gene. Our data show that the regulatory mechanisms that control tubulin pool levels in the Drosophila male germ line differ from those observed in cultured animal somatic cells. Finally, expression of transgenic constructs is consistent with early cessation of X chromosome expression in Drosophila spermatogenesis.

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Section: Early Cessation Of X-chromosome Expression In the Drosophilumentioning

confidence: 99%

Regulation of β‐tubulin function and expression in Drosophila spermatogenesis

et al. 1995

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“…It may thus be possible to use the analysis of X-chromatin for the diagnosis of abnormalities in the number of X chromosomes (for reviews see Barr and Carr, 1962;Grumbach et ai., 1963;Barr, 1966;Hamerton, 1969 and. The number of X-chromatin bodies in a cell with a diploid autosome set is at most one less than the number of X chromosomes present.…”

Section: X-chromatinmentioning

confidence: 99%

Methods in Human Cytogenetics

Ma¹

1974

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The paranucleolar structure, accessory body of cajal, sex chromatin, and related structures in nuclei of rat trigeminal neurons: A cytochemical and ultrastructural study

1969

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Comparative light and electron microscopic study of nuclei in rat trigeminal neurons identified two structures which are the ultrastructural equivalent of the paranucloelar structure and the accessory body of Cajal, two nucleoplasmic structures previously demonstrated in other neurons by light microscope silver staining methods. Ultrastructural evidence indicates that the dense component of the nucleolus is converted into the paranucleolar structure, which then detaches from the nucleolar surface to lie free in the nucleoplasm as the accessory body of Cajal. The cytochemistry, ultrastructure, and antimonate reactivity of the paranucleolar structure and accessory body were identical. Both structures lacked cytochemically demonstrable DNA, RNA, or basic protein.The neuronal nuclei also contained Feulgen-positive sex chromatin bodies that adhered to the nucleolus, the nuclear membrane, or to both of these structures in specimens of female but not male rats. The ultrastructure and antimonate reactivity of these bodies closely resembled that of heterochromatin clumps but differed markedly from that of the paranucleolar structures and accessory bodies.Additional structures characterized ultrastructurally included patches, granular bodies, and flakes. These structures, like the paranucleolar structure and the accessory body of Cajal, are apparently unique to nuclei of neurons. Cytochemical methods showed that the patches contained basic protein but no nucleic acid.Light microscope silver staining methods have visualized structures of undetermined significance in the nucleoplasm of neurons. One of these, "the accessory body of Cajal," is an argyrophilic, Feulgennegative, nonbasophilic structure. These round bodies, measuring about 1 LI in diameter, are located between the nucleolus and nuclear membrane (Ramon y Cajal, '03; Lindsay and Barr, '55; Haggar, '57; Thompson, Haggar and Ban, '57). Another argyrophilic, Feulgen-negative, nonbasophilic body in neuronal nuclei is "the paranucleolar structure," which differs from the accessory body of Cajal by its attachment to the nucleolus and its hemispherical or concavoconvex shape (Haggar, '57; Thompson, Haggar and Barr, '57). Although it has been speculated that the paranucleolar structure may derive from the nucleolus and be converted to the accessory body of Cajal (Haggar, '57), direct evidence is lacking for such interrelationships. ANAT. REC., 164: 403-432.An ultrastructural counterpart of the accessory body of Cajal or the paranucleolar structure has not been determined. The present study describes cytochemical and ultrastructural features of two types of nuclear bodies in neurons of rat trigeminal ganglia. Evidence is presented that one of these bodies corresponds to the accessory body of Cajal and the other to the paranucleolar structure. Observations were also made on structures at the nucleolar surface and free in the nucleoplasm that might be confused with the paranucleolar structure and the accessory body of Cajal. In addition, this investigation undertakes ...

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The Significance of the Sex Chromatin*

Cited by 30 publications

References 198 publications

Regulation of β‐tubulin function and expression in Drosophila spermatogenesis

Regulation of β‐tubulin function and expression in Drosophila spermatogenesis

Methods in Human Cytogenetics

The paranucleolar structure, accessory body of cajal, sex chromatin, and related structures in nuclei of rat trigeminal neurons: A cytochemical and ultrastructural study

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