Dynamics of nuclear matrix attachment regions during 5th instar posterior silk gland development in Bombyx mori

Abstract

Background Chromatin architecture is critical for gene expression during development. Matrix attachment regions (MARs) control and regulate chromatin dynamics. The position of MARs in the genome determines the expression of genes in the organism. In this study, we set out to elucidate how MARs temporally regulate the expression of the fibroin heavy chain (FIBH) gene during development. We addressed this by identifying MARs and studying their distribution and differentiation, in the posterior silk glands of Bombyx mori during 5th instar development. Results Of the MARs identified on three different days, 7.15% MARs were common to all 3 days, whereas, 1.41, 19.27 and 52.47% MARs were unique to day 1, day 5, and day 7, respectively highlighting the dynamic nature of the matrix associated DNA. The average chromatin loop length based on the chromosome wise distribution of MARs and the distances between these MAR regions decreased from day 1 (253.91 kb) to day 5 (73.54 kb) to day 7 (39.19 kb). Further significant changes in the MARs in the vicinity of the FIBH gene were found during different days of 5th instar development which implied their role in the regulation and expression of the FIBH gene. Conclusions The presence of MARs in the flanking regions of genes found to exhibit differential expression during 5th instar development indicates their possible role in the regulation of their expression. This reiterates the importance of MARs in the genomic functioning as regulators of the molecular mechanisms in the nucleus. This is the first study that takes into account the tissue specific genome-wide MAR association and the potential role of these MARs in developmentally regulated gene expression. The current study lays a foundation to understand the genome wide regulation of chromatin during development.

Transposable elements as scaffold/matrix attachment regions: shaping organization and functions in genomes

“…Only two studies of genome-wide mapping of S/MAR investigate their dynamics during embryonic development or cellular differentiation ( Chunduri et al, 2022 ; Sureka et al, 2022 ). These studies, for the first time, uncovered that these attachment points can be categorized as dynamic or stable (Core-MARs) ( Figure 1 ).…”

CRISPR/Cas9-Mediated Editing of BmEcKL1 Gene Sequence Affected Silk Gland Development of Silkworms (Bombyx mori)

“…Cyclins B and E and Scr have been shown to be involved in this process [17,18]. In the larval stage, the silk gland no longer undergoes mitosis and increases its DNA content only through intranuclear replication [19,20]; it has been shown that Let7 MicroRNAs (Let7) knockout promotes intranuclear replication in silk gland cells [21,22]. Apoptosis in the silk gland is thought to be regulated by ecdysteroids (insect growth and molting hormones) and involves both apoptosis and autophagy [23][24][25].…”