The localization of LAP2 beta during pronuclear formation in bovine oocytes after fertilization or activation

Emerin Is Required for Proper Nucleus Reassembly after Mitosis: Implications for New Pathogenetic Mechanisms for Laminopathies Detected in EDMD1 Patients

Emerin is an essential LEM (LAP2, Emerin, MAN1) domain protein in metazoans and an integral membrane protein associated with inner and outer nuclear membranes. Mutations in the human EMD gene coding for emerin result in the rare genetic disorder: Emery⁻Dreifuss muscular dystrophy type 1 (EDMD1). This disease belongs to a broader group called laminopathies-a heterogeneous group of rare genetic disorders affecting tissues of mesodermal origin. EDMD1 phenotype is characterized by progressive muscle wasting, contractures of the elbow and Achilles tendons, and cardiac conduction defects. Emerin is involved in many cellular and intranuclear processes through interactions with several partners: lamins; barrier-to-autointegration factor (BAF), β-catenin, actin, and tubulin. Our study demonstrates the presence of the emerin fraction which associates with mitotic spindle microtubules and centrosomes during mitosis and colocalizes during early mitosis with lamin A/C, BAF, and membranes at the mitotic spindle. Transfection studies with cells expressing EGFP-emerin protein demonstrate that the emerin fusion protein fraction also localizes to centrosomes and mitotic spindle microtubules during mitosis. Transient expression of emerin deletion mutants revealed that the resulting phenotypes vary and are mutant dependent. The most frequent phenotypes include aberrant nuclear shape, tubulin network mislocalization, aberrant mitosis, and mislocalization of centrosomes. Emerin deletion mutants demonstrated different chromatin binding capacities in an in vitro nuclear assembly assay and chromatin-binding properties correlated with the strength of phenotypic alteration in transfected cells. Aberrant tubulin staining and microtubule network phenotype appearance depended on the presence of the tubulin binding region in the expressed deletion mutants. We believe that the association with tubulin might help to "deliver" emerin and associated membranes to decondensing chromatin. Preliminary analyses of cells from Polish patients with EDMD1 revealed that for several mutations thought to be null for emerin protein, a truncated emerin protein was present. We infer that the EDMD1 phenotype may be strengthened by the toxicity of truncated emerin expressed in patients with certain nonsense mutations in EMD.

Time-lapse observation and transcriptome analysis of a case with repeated multiple pronuclei after IVF/ICSI

PURPOSE

The purpose of this study was to investigate the cause of repeated multipronucleus (MPN) formation in zygotes in a patient after both in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).

METHOD

This is a case study. A patient had unexplained primary infertility with recurring total MPN zygotes after IVF and ICSI cycles. Time-lapse monitoring of pronucleus formation was carried out. Embryos developed from MPN zygotes were analyzed by fluorescence in situ hybridization (FISH). Single-cell RNA-seq analysis was used to identify gene expression profiles of the patient's oocyte and zygote, and these were compared to the data from oocytes and zygotes from donors with normal fertilization (patient, n = 1; donors, n = 4). Oocyte-specific genes with differential expression were selected by the Amazonia!

DATABASE

RESULTS

From time-lapse analysis, we observed the formation of multiple micronuclei near the site of the second polar body extrusion. These micronuclei migrated, expanded, and juxtaposed with the male pronucleus leading to a multipronucleus. None of these MPN zygotes could develop to the blastocyst stage, and FISH analysis revealed a chaotic chromosomal complement in the arrested embryos. RNA-seq analysis showed 113 differentially expressed genes (DEGs) between the patient and the donor oocytes and zygotes. Moreover, 25 of the 113 DEGs were unique or highly expressed in oocytes and early embryos. From 25 DEGs, three genes, DYNC2LI1, NEK2, and CCNH, which are involved in meiosis and the chromosome separation process, were further validated by real-time PCR.

CONCLUSION

We identified several candidate genes affecting pronucleus formation as a new cause of infertility.