کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2176088 1549577 2006 15 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Establishment of animal–vegetal polarity during maturation in ascidian oocytes
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی بیولوژی سلول
پیش نمایش صفحه اول مقاله
Establishment of animal–vegetal polarity during maturation in ascidian oocytes
چکیده انگلیسی

Mature ascidian oocytes are arrested in metaphase of meiosis I (Met I) and display a pronounced animal–vegetal polarity: a small meiotic spindle lies beneath the animal pole, and two adjacent cortical and subcortical domains respectively rich in cortical endoplasmic reticulum and postplasmic/PEM RNAs (cER/mRNA domain) and mitochondria (myoplasm domain) line the equatorial and vegetal regions. Symmetry-breaking events triggered by the fertilizing sperm remodel this primary animal–vegetal (a–v) axis to establish the embryonic (D–V, A–P) axes. To understand how this radial a–v polarity of eggs is established, we have analyzed the distribution of mitochondria, mRNAs, microtubules and chromosomes in pre-vitellogenic, vitellogenic and post-vitellogenic Germinal Vesicle (GV) stage oocytes and in spontaneously maturing oocytes of the ascidian Ciona intestinalis. We show that myoplasm and postplasmic/PEM RNAs move into the oocyte periphery at the end of oogenesis and that polarization along the a–v axis occurs after maturation in several steps which take 3–4 h to be completed. First, the Germinal Vesicle breaks down, and a meiotic spindle forms in the center of the oocyte. Second, the meiotic spindle moves in an apparently random direction towards the cortex. Third, when the microtubular spindle and chromosomes arrive and rotate in the cortex (defining the animal pole), the subcortical myoplasm domain and cortical postplasmic/PEM RNAs are excluded from the animal pole region, thus concentrating in the vegetal hemisphere. The actin cytoskeleton is required for migration of the spindle and subsequent polarization, whereas these events occur normally in the absence of microtubules. Our observations set the stage for understanding the mechanisms governing primary axis establishment and meiotic maturation in ascidians.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Developmental Biology - Volume 290, Issue 2, 15 February 2006, Pages 297–311
نویسندگان
, , ,