Mitochondrial reorganization during resumption of arrested meiosis in the mouse oocyte

TLDR

Reactivated meiosis in mouse oocytes involves coordinated nuclear and cytoplasmic reorganizations over 14 hours, studied both in vivo and in vitro. The study aims to determine whether rapid mitochondrial translocations during meiosis concentrate mitochondria to support ATP‑dependent localized activities. Live‑cell microscopy with DIC and fluorescent probes revealed two mitochondrial translocations linked to nuclear maturation stages. TEM confirmed that mitochondria move to the perinuclear region during first metaphase spindle formation and disperse during first polar body extrusion, and frequency analyses of over 2,900 oocytes indicate that these redistributions are a normal and likely essential feature of reactivated meiosis.

Abstract

Abstract Correlated nuclear and cytoplasmic reorganizations during the 14 hr of reactivated meiosis in vivo and in vitro were examined in the laboratory mouse. Observations of living oocytes by differential interference contrast microscopy, and by fluorescent microscopy with nontoxic mitochondrial and DNA‐specific probes, enabled us to determine that the major cytoplasmic reorganization involved two mitochondrial translocations associated with two stages of nuclear maturation. These observations were confirmed at the fine structural level by parallel transmission electron microscopy. Mitochondria translocate to the perinuclear region during formation of the first metaphase spindle and subsequently disperse during abstriction of the first polar body. Determinations of frequency of maturation in more than 2,900 normal oocytes, and in more than 1,100 oocytes in which germinal vesicle breakdown was reversibly inhibited, indicated that mitochondrial redistributions are a normal and probably necessary feature of reactivated meiosis in the laboratory mouse. We suggest that these two rapid translocations serve to concentrate mitochondria for localized activities that require elevated levels of adenosine triphosphate.