A S MUKHERJEE

W BEERMANN

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Nature

In many sexually reproducing species, sex is determined by cytologically distinguishable ‘sex chromosomes’. The popular view is that the consequence of heteromorphic sex chromosomes is detrimental, and evolutionary emergence of dosage compensation mechanism is expected for two fold upregulation of X linked genes in order to restore the balance for the haplo-X in the sex against the diplo X of the other. Since, male and female share nearly identical genome in most animals, and since antagonistic selection operate for the expression divergence of the sex biased genes between sexes for mating type distinction, dosage compensation system is evolved in many species to link global transcription profile of the genome through histone variants and epigenetic modification of the genes for driving sex determination function. Whole genome transcriptome analyses and the investigations on the profiling of accessible chromatin components in male and female at different phase of development of Drosophila, C. elegans and mammal revealed that 50–60% X and autosomal genes of the genomes are expressed under sex specific selection through allelic bias (except some required dosage sensitive genes) expression, ranging from absent to complete compensation. The review focuses the recent development of dosage compensation research and illustrates its roles in sex chromosome evolution and sexual dimorphism in Drosophila, C. elegans and mammals. © 2017, Archana Sharma Foundation of Calcutta.

Nucleus (India)

Dosage compensation and its roles in evolution of sex chromosomes and phenotypic dimorphism: lessons from Drosophila, C.elegans and mammals

Epigeneticmodifications of entireXchromosome(s) are adapted in many animals to keep balance of gene dose difference between sexes possessing different number of sex chromosomes required for sex determination. Different animals have adapted different mechanisms for epigenetic regulation of X chromosomal expression depending on 'demasculinization' of the X chromosome. The epigenetic programming for dosage compensation in Drosophila is to hyperactivate the male X chromosome by histone H4 modification. In Caenorhabditis elegans, both X chromosomal histones of hermaphrodite are methylated for down regulation of X linked gene expression.Mammals have developed a system of epigenetic modification for both upregulation and repression of X chromosomal genes for dosage compensation. In recent years, epigenetic modifications that occur during male meiosis are characterized with special attention on events that define meiotic sex chromosome inactivation. As data accumulate, noval features of dosage compensation processes of different animals are also gaining attention. This review highlights the crucial roles of germline X chromosomal organization, that are potentially relevant to epigenetic modulation of somatic dosage compensation in the three animals. © Archana Sharma Foundation of Calcutta 2012.

Evolutionary origin of chromatin remodeling for dosage compensation: Lessons from epigenetic modifications of X chromosomes in germ cells of drosophila, C. elegans and mammals

We studied by autoradiography the replication and transcription patterns of polytene X chromosomes in different segmental aneuploid and hyperploid conditions in a constant diploid autosomal background. In all karyotypes, the patterns of X chromosome compaction and DNA synthesis were observed to be set strictly either at a "male-level" or a "female-level". Addition of X-fragments to 1X progeny exceeding a certain limit (62% with proximal duplication) changed the pattern of chromatin compaction and replication of X chromosomes from male to female level, while similar additional X-fragments had no comparable effect on 2X hyperdiploids. In contrast, different levels of X-transcription per segment were observed in these aneuploids with variable X-load and in consequence, an equivalent amount of total X-transcription (relative to autosomal transcription) was visualized. These findings while favour a positive correlation between the state of chromosome compaction and replication patterns, are at odds with the idea that for an altered level of transcription, a modulation in the state of chromosome compaction and replication is an obligatory pre-requisite. © 1990 Indian Academy of Sciences.

Proceedings: Animal Sciences

Interrelationship between the states of chromosome compaction, replication and transcription patterns in the polytene-X chromosome of Drosophila melanogaster

The chromatin template activity of the fixed polytene chromosomes of larval salivary glands of Drosophila melanogaster strains trisomic for the entire left arm of chromosome 2 or chromosome 3 was monitored using 3H-UTP and Escherichia coli RNA polymerase holoenzyme. The three doses of active loci in the trisomic strains were found to synthesize 30%-40% more RNA than the normal double dose of the same region in the wild-type male and female. The higher template activity of the genes on 2L or 3L in the trisomic strains, had no marked effect on the chromatin template activity of the X chromosomes of the male or female. These results suggest that (1) the template activity of an autosomal gene must be viewed as a basal level, comparable to the female X-chromosome and (2) hyperploids for any region of chromosome 2L or 3L have very little or no recognisable influence on X chromosomal organisation. © 1986 Springer-Verlag.

Chromosoma

Dosage compensation and template organisation in Drosophila: In situ transcriptional analysis of the chromatin template activity of the X and autosomes of D. melanogaster strains trisomic for the left arm of the second and third chromosomes

The transcriptional competence of the X-chromosome of a mutant strain of Drosophila melanogaster, [in(1)BM2 (reinverted)], and of hyperploid derivatives with different additional segments of the X-chromosome has been examined. The single X in the mutant male shows twice as much puffiness and RNA synthesis as does that in the normal male, revealing a level of X-coded activity in addition to the normal male and female levels. Feulgen cytophotometry reveals no duplication of DNA content in the mutant X. When duplication for the segments 1A-3E, 9A-20F, 11A-20F and 16A-20F of the X-chromosome are combined in the male with the mutant chromosome, the super-hyperactivity of the mutant X is completely abolished. In combination with the Bs. Y duplication, which contains 16A7-B2, the two-fold activity is also completely suppressed. The mutant chromosome can appear in three discrete manifestations, namely, highly flabby, intermittently flabby and normal, suggesting a leaky nature of the mutant. The effect is also temperature-sensitive. Our results suggest that there may be a modulator gene complex (M+) in the 16A7-B2 region as well as regulators elsewhere on the X, which in combination influence the hyperactivity of the male X in Drosophila. We suggest that the In(1)BM2 (reinverted) chromosome carries a hypomorphic mutation of M+(Mm). The results presented here and earlier data on various X-chromosomal and autosomal hyperploids are discussed in the light of a model for dosage compensation in Drosophila. © 1986, Cambridge University Press. All rights reserved.

Fulltext

Genetical Research

A different level of X-chromosomal transcription in an In(1)BM2 (reinverted) strain and in its hyperploid derivatives resolves an X-coded regulatory activity for dosage compensation in Drosophila

Journal	Nature
Publisher	-
ISSN	0028-0836