CLINICAL CONFERENCE

PEDIATRICS ◽  
1957 ◽  
Vol 20 (4) ◽  
pp. 740-746
Author(s):  
Melvin M. Grumbach
Keyword(s):  
Sex Difference ◽  
Sex Chromosome ◽  
Good Evidence ◽  
Polymorphonuclear Neutrophils ◽  
Vaginal Mucosa ◽  
Simple Method ◽  
X Chromosomes ◽  
Cytologic Examination ◽  
Sex Development ◽  
Sex Chromatin

Dr. Grumbach: Barr and associates have demonstrated that in the human the majority of somatic cells of females contain a conspicuous, heterochromatic mass of chromatin in the resting nuclei. Their discovery of a sex-difference in intermitotic nuclei of a number of vertebrate species, including man, has provided a relatively simple method for assessing the sex-chromosome constitution. This chromatin mass is about 1 micron in diameter and often plano-convex in configuration. It is usually located against the inner surface of the nuclear membrane and contains desoxyribonucleic acid. In males, a comparable chromatin mass is rarely found, never in more than a few per cent of the nuclei. There is good evidence that this so-called "sexchromatin" represents the fusion of heterochromatic portions of two X-chromosomes. The sex chromatin can be conveniently determined by examination of specimens of skin obtained by biopsy (Fig. 1). Recently, more practical methods for determining cytologic sex have been described employing smears from readily available tissues, such as the oral and vaginal mucosa (Fig. 2) and the blood. Davidson and Smith have shown that there is a sex difference in the morphology of polymorphonuclear neutrophils. Cytologic examination of chromosomal sex has provided an important tool for the investigation of anomalies of sex development. Apart from its ancillary role in diagnosis, cytologic examination of sex chromatin has made a significant contribution to our understanding of the disordered development in these afflictions. However, the results of this determination should not be regarded as an especial indication of the psychosexual orientation of patients with such abnormalities, nor, in the case of infants, of the sex to which they should be assigned.

SEXUAL DIMORPHISM IN INTERPHASE NUCLEI OF THE LION, FELIS LEO

1965 ◽  
Vol 43 (3) ◽  
pp. 439-445
Author(s):  
Keith L. Moore
Keyword(s):  
Sexual Dimorphism ◽  
Nucleic Acid ◽  
Sex Difference ◽  
Nuclear Membrane ◽  
Sex Chromosome ◽  
Cell Types ◽  
Interphase Nuclei ◽  
X Chromosomes ◽  
Sex Chromatin ◽  
Inner Surface

A sex difference is present in the structure of interphase nuclei of somatic cells in a variety of tissues of the lion. In the female, but not in the male, there is a special mass of chromatin, the sex chromatin, which stands out from the general particulate chromatin. In neurons the sex chromatin is usually located adjacent to the nucleolus, but in other cell types it nearly always lies against the inner surface of the nuclear membrane. The sex chromatin has the cytochemical properties of desoxypentose nucleic acid and is probably derived from heterochromatic regions of one of the X-chromosomes of the female's sex chromosome complex. A mass similar to the sex chromatin of females is rarely encountered in nuclei of males. The sexual dimorphism present in interphase nuclei of the lion is similar to that described previously in other carnivores and in primates.

The Mental Implications of Sex Chromosome Aberrations

1970 ◽  
Vol 117 (539) ◽  
pp. 353-363 ◽  
Author(s):  
Hans Forssman
Keyword(s):  
Mental Health ◽  
Cell Lines ◽  
Social Adjustment ◽  
Chromosome Aberrations ◽  
Sex Chromosome ◽  
Chromosome Complement ◽  
X Chromosomes ◽  
Unfavourable Effect ◽  
Sex Chromatin ◽  
Large Sections

I have chosen as the subject for my Blake Marsh Lecture the influence of sex chromosome aberrations on intelligence, mental health and social adjustment. This subject provides a fascinating example of how a branch of research, beginning in the field of mental retardation, arrived at discoveries which proved to be of significance to quite other fields of psychiatry. Ten years ago we learned that sex-chromatin-positive males, that is, males with additional X chromosomes, at least in some cell lines, were more often encountered among the intellectually retarded than among the average population of males. Shortly after this we learned that the same was true of women with double Barr bodies, that is, women with more than the usual two X chromosomes, at least in some cell lines. Today we have facts showing that an abnormal sex chromosome complement may have an unfavourable effect on mental health, and this in several different ways; thus we know that it may contribute to the development of functional psychoses, and may even influence such a complex variable of behaviour as our ability to adapt ourselves to the laws of the community. Myself, I am convinced that study of aberrations in the sex chromosomes will prove to have a radical effect on large sections of psychiatric thinking.

scholarly journals Bisection of the X chromosome disrupts the initiation of chromosome silencing during meiosis in Caenorhabditis elegans

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yisrael Rappaport ◽  
Hanna Achache ◽  
Roni Falk ◽  
Omer Murik ◽  
Oren Ram ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Rna Polymerase Ii ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Transcription Analysis ◽  
X Chromosomes ◽  
Unique Character ◽  
Active Transcription ◽  
Heterogametic Sex

AbstractDuring meiosis, gene expression is silenced in aberrantly unsynapsed chromatin and in heterogametic sex chromosomes. Initiation of sex chromosome silencing is disrupted in meiocytes with sex chromosome-autosome translocations. To determine whether this is due to aberrant synapsis or loss of continuity of sex chromosomes, we engineered Caenorhabditis elegans nematodes with non-translocated, bisected X chromosomes. In early meiocytes of mutant males and hermaphrodites, X segments are enriched with euchromatin assembly markers and active RNA polymerase II staining, indicating active transcription. Analysis of RNA-seq data showed that genes from the X chromosome are upregulated in gonads of mutant worms. Contrary to previous models, which predicted that any unsynapsed chromatin is silenced during meiosis, our data indicate that unsynapsed X segments are transcribed. Therefore, our results suggest that sex chromosome chromatin has a unique character that facilitates its meiotic expression when its continuity is lost, regardless of whether or not it is synapsed.

scholarly journals Absence of X-chromosome dosage compensation in the primordial germ cells of Drosophila embryos

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryoma Ota ◽  
Makoto Hayashi ◽  
Shumpei Morita ◽  
Hiroki Miura ◽  
Satoru Kobayashi
Keyword(s):  
X Chromosome ◽  
Germ Cells ◽  
Dosage Compensation ◽  
Sex Chromosome ◽  
Primordial Germ Cells ◽  
Histone H4 ◽  
X Chromosomes ◽  
Essential Components ◽  
Msl Complex ◽  
Male Specific

AbstractDosage compensation is a mechanism that equalizes sex chromosome gene expression between the sexes. In Drosophila, individuals with two X chromosomes (XX) become female, whereas males have one X chromosome (XY). In males, dosage compensation of the X chromosome in the soma is achieved by five proteins and two non-coding RNAs, which assemble into the male-specific lethal (MSL) complex to upregulate X-linked genes twofold. By contrast, it remains unclear whether dosage compensation occurs in the germline. To address this issue, we performed transcriptome analysis of male and female primordial germ cells (PGCs). We found that the expression levels of X-linked genes were approximately twofold higher in female PGCs than in male PGCs. Acetylation of lysine residue 16 on histone H4 (H4K16ac), which is catalyzed by the MSL complex, was undetectable in these cells. In male PGCs, hyperactivation of X-linked genes and H4K16ac were induced by overexpression of the essential components of the MSL complex, which were expressed at very low levels in PGCs. Together, these findings indicate that failure of MSL complex formation results in the absence of X-chromosome dosage compensation in male PGCs.

scholarly journals Red queen's race: rapid evolutionary dynamics of an expanding family of meiotic drive factors and their hpRNA suppressors

2021 ◽  
Author(s):  
Jeffrey Vedanayagam ◽  
Ching-Jung Lin ◽  
Eric C. Lai
Keyword(s):  
Evolutionary Dynamics ◽  
Sex Chromosome ◽  
De Novo ◽  
Independent Set ◽  
Meiotic Drive ◽  
Sperm Chromatin ◽  
Arms Races ◽  
X Chromosomes ◽  
Selfish Genetic Elements ◽  
Satellite Repeats

Meiotic drivers are a class of selfish genetic elements that are widespread across eukaryotes. Their activities are often detrimental to organismal fitness and thus trigger drive suppression to ensure fair segregation during meiosis. Accordingly, their existence is frequently hidden in genomes, and their molecular functions are little known. Here, we trace evolutionary steps that generated the Dox meiotic drive system in Drosophila simulans (Dsim), which distorts male:female balance (sex-ratio) by depleting male progeny. We show that Dox emerged via stepwise mobilization and acquisition of portions of multiple D. melanogaster genes, including the sperm chromatin packaging gene protamine. Moreover, we reveal novel Dox homologs in Dsim and massive, recent, amplification of Dox superfamily genes specifically on X chromosomes of its closest sister species D. mauritiana (Dmau) and D. sechellia (Dsech). The emergence of Dox superfamily genes is tightly associated with 1.688 family satellite repeats that flank de novo genomic copies. In concert, we find coordinated emergence and diversification of autosomal hairpin RNA/siRNAs loci that target subsets of Dox superfamily genes across simulans clade species. Finally, an independent set of protamine amplifications the Y chromosome of D. melanogaster indicates that protamine genes are frequent and recurrent players in sex chromosome dynamics. Overall, we reveal fierce genetic arms races between meiotic drive factors and siRNA suppressors associated with recent speciation.

scholarly journals A new sympatric region for distinct karyotypic forms of Hoplias malabaricus (Pisces, Erythrinidae)

2006 ◽  
Vol 66 (1b) ◽  
pp. 205-210 ◽  
Author(s):  
G. G. Born ◽  
L. A. C. Bertollo
Keyword(s):  
Sex Difference ◽  
Sex Chromosomes ◽  
Diploid Number ◽  
Sex Chromosome ◽  
Minas Gerais ◽  
Female Specimen ◽  
Male Specimen ◽  
Hoplias Malabaricus ◽  
Sex Chromosome System ◽  
Sympatric Cytotypes

Specimens of Hoplias malabaricus from Lagoa Carioca, an isolated lake of the Rio Doce State Park (state of Minas Gerais, Brazil), were cytogenetically studied. The diploid number was found to be constant, i.e., 2n = 42 chromosomes, although two karyotypic forms were found: karyotype A, characterized by 22M + 20SM chromosomes, observed only in a male specimen, and karyotype B, characterized by 24M + 16SM + 2ST and 24M + 17SM + 1ST chromosomes in female and male specimens, respectively. This sex difference found in karyotype B is related to an XX/XY sex chromosome system. Another female specimen of H. malabaricus, also carrying karyotype A, had previously been found in the same lake. The available data indicate that two sympatric cytotypes of H. malabaricus exist in the Lagoa Carioca, with cytotype A occurring at a lower frequency and differing from cytotype B by undifferentiated sex chromosomes.

scholarly journals Parallel Universes for Models of X Chromosome Dosage Compensation in Drosophila: A Review

2016 ◽  
Vol 148 (1) ◽  
pp. 52-67 ◽  
Author(s):  
James A. Birchler
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Sex Chromosome ◽  
Fold Increase ◽  
Molecular Data ◽  
X Chromosomes ◽  
Histone Modifiers ◽  
Parallel Universes ◽  
Msl Complex ◽  
High Level

Dosage compensation in Drosophila involves an approximately 2-fold increase in expression of the single X chromosome in males compared to the per gene expression in females with 2 X chromosomes. Two models have been considered for an explanation. One proposes that the male-specific lethal (MSL) complex that is associated with the male X chromosome brings histone modifiers to the sex chromosome to increase its expression. The other proposes that the inverse effect which results from genomic imbalance would tend to upregulate the genome approximately 2-fold, but the MSL complex sequesters histone modifiers from the autosomes to the X to mute this autosomal male-biased expression. On the X, the MSL complex must override the high level of resulting histone modifications to prevent overcompensation of the X chromosome. Each model is evaluated in terms of fitting classical genetic and recent molecular data. Potential paths toward resolving the models are suggested.

scholarly journals A second X chromosome contributes to resilience in a mouse model of Alzheimer’s disease

2020 ◽  
Vol 12 (558) ◽  
pp. eaaz5677 ◽  
Author(s):  
Emily J. Davis ◽  
Lauren Broestl ◽  
Samira Abdulai-Saiku ◽  
Kurtresha Worden ◽  
Luke W. Bonham ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Testicular Development ◽  
X Chromosomes ◽  
Model Of Alzheimer’S Disease ◽  
Preclinical Ad ◽  
Brain Expression

A major sex difference in Alzheimer’s disease (AD) is that men with the disease die earlier than do women. In aging and preclinical AD, men also show more cognitive deficits. Here, we show that the X chromosome affects AD-related vulnerability in mice expressing the human amyloid precursor protein (hAPP), a model of AD. XY-hAPP mice genetically modified to develop testicles or ovaries showed worse mortality and deficits than did XX-hAPP mice with either gonad, indicating a sex chromosome effect. To dissect whether the absence of a second X chromosome or the presence of a Y chromosome conferred a disadvantage on male mice, we varied sex chromosome dosage. With or without a Y chromosome, hAPP mice with one X chromosome showed worse mortality and deficits than did those with two X chromosomes. Thus, adding a second X chromosome conferred resilience to XY males and XO females. In addition, the Y chromosome, its sex-determining region Y gene (Sry), or testicular development modified mortality in hAPP mice with one X chromosome such that XY males with testicles survived longer than did XY or XO females with ovaries. Furthermore, a second X chromosome conferred resilience potentially through the candidate gene Kdm6a, which does not undergo X-linked inactivation. In humans, genetic variation in KDM6A was linked to higher brain expression and associated with less cognitive decline in aging and preclinical AD, suggesting its relevance to human brain health. Our study suggests a potential role for sex chromosomes in modulating disease vulnerability related to AD.

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