Actin Colocalization with Metaphase Chromosomes of the Second Meiosis in Ovulated Mouse Oocytes

Abstract EN

Functional interrelation of nuclear actin with transcriptional active chromatin in the interphase nucleus was reliably established in numerous experiments, but the relationship between actin and transcriptional silent chromatin is still unclear.

We examined localization area of the second meiotic division metaphase plate in ovulated mouse oocytes with the aim to study the possibility of actin-chromatin colocalization and uncovering the distribution patterns of different functional forms of actin near the metaphase chromosomes.

Confocal microscopy and probes for actin that are distinguished from each other by the mechanism of actin binding (TRITC-phalloidin, fluorescent DNase-I, and antibodies against fragment of C-terminal and fragment of N-terminal domain of actin) were used for actin visualization.

Despite the fact that TRITC-phalloidin could not detect F-actin in the area of metaphase plate, oocytes staining with antibody against fragment of the actin N-terminal domain demonstrates the presence near the metaphase chromosomes of some spindle-like structure composed of actin filaments.

Among all used probes for actin, only the antibody against fragment of the C-terminal domain detected accurate actin colocalization with metaphase chromosomes.

We conclude that this antibody labeled noncanonical form of the nuclear actin existing in long-term association with highly condensed chromatin.