Biology subjects

El Khattabi, L.

Publications and source records attributed to El Khattabi, L..

3 recordsLinked to original sources

bioRxiv2022

The histone methyltransferase DOT1L regulates chromatin reorganization and gene expression during the postmeiotic differentiation of male germ cells

Spermatozoa have a unique genome organization: their chromatin is almost completely devoid of histones and is formed instead of protamines which confer a high level of compaction and preserve paternal genome integrity until fertilization. Histone-to-protamine transition takes place in spermatids and is indispensable for the production of functional sperm. Here we show that the H3K79-methyltransferase DOT1L controls spermatid chromatin remodelling and subsequent reorganization and compaction of spermatozoon genome. Using a mouse model in which Dot1l is knocked-out (KO) in postnatal male germ cells, we found that Dot1l-KO sperm chromatin is less compact and has an abnormal content, characterized by the presence of transition proteins, immature protamine 2 forms and a higher level of histones. Proteomics and transcriptomics analyses performed on spermatids reveal that Dot1l-KO modifies the chromatin prior to histone removal, and leads to the deregulation of genes involved in flagellum formation and apoptosis during spermatid differentiation. As a consequence of these chromatin and gene expression defects, Dot1l-KO spermatozoa have less compact heads and are less motile which results in impaired fertility.

molecular biology↗

bioRxiv2020

Structure of the Mammalian Mediator

The Mediator complex plays an essential and multi-faceted role in regulation of RNA polymerase II transcription in all eukaryotes. Structural analysis of yeast Mediator has provided an understanding of the conserved core of the complex and its interaction with RNA polymerase II but failed to reveal the structure of the Tail module that contains most subunits targeted by activators and repressors. Here we present a molecular model of mammalian (Mus musculus) Mediator, derived from a 4.0 [A] resolution cryo-EM map of the complex. The mammalian Mediator structure reveals that the previously unresolved Tail module, which includes a number of metazoan specific subunits, interacts extensively with core Mediator and has the potential to influence its conformation and interactions.

cell biology↗

bioRxiv2020

Next generation cytogenetics: genome-imaging enables comprehensive structural variant detection for 100 constitutional chromosomal aberrations in 85 samples

Chromosomal aberrations and structural variations are a major cause of human genetic diseases. Their detection in clinical routine still relies on standard cytogenetics, karyotyping and CNV-microarrays, in spite of the low resolution of the first one and the inability to detect neither balanced SVs nor to provide the genomic localization or the orientation of duplicated segments, of the latter. We here investigated the clinical utility of high resolution optical mapping by genome imaging for patients carrying known chromosomal aberrations in a context of constitutional conditions. For 85 samples, ultra-high molecular weight gDNA was isolated either from blood or cultured cells. After labeling, DNA was processed and imaged on the Saphyr instrument (Bionano Genomics). A de novo genome assembly was performed followed by SV and CNV calling and annotation. Results were compared to known aberrations from standard-of-care tests (karyotype, FISH and/or CNV-microarray). In total, we analyzed 100 chromosomal aberrations including 7 aneuploidies, 35 translocations, 6 inversions, 2 insertions, 39 copy number variations (20 deletions and 19 duplications), 6 isochromosomes, 1 ring chromosome and 4 complex rearrangements. High resolution optical mapping reached 100% concordance compared to standard assays for all aberrations with non-centromeric breakpoints. Our study demonstrates the ability of high resolution optical mapping to detect almost all types of chromosomal aberrations within the spectrum of karyotype, FISH and CNV-microarray. These results highlight its potential to replace these techniques, and provide a cost-effective and easy-to-use technique that would allow for comprehensive detection of chromosomal aberrations.

genetics↗