کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2174063 1093780 2009 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
D quadrant specification in the leech Helobdella: Actomyosin contractility controls the unequal cleavage of the CD blastomere
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی بیولوژی سلول
پیش نمایش صفحه اول مقاله
D quadrant specification in the leech Helobdella: Actomyosin contractility controls the unequal cleavage of the CD blastomere
چکیده انگلیسی

The unequal division of the CD blastomere at second cleavage is critical in establishing the second embryonic axis in the leech Helobdella, as in other unequally cleaving spiralians. When CD divides, the larger D and smaller C blastomeres arise invariantly on the left and right sides of the embryo, respectively. Here we show that stereotyped cellular dynamics, including the formation of an intercellular blastocoel, culminate in a morphological left–right asymmetry in the 2-cell embryo, which precedes cytokinesis and predicts the chirality of the second cleavage. In contrast to the unequal first cleavage, the unequal second cleavage does not result from down-regulation of one centrosome, nor from an asymmetry within the spindle itself. Instead, the unequal cleavage of the CD cell entails a symmetric mitotic apparatus moving and anisotropically growing rightward in an actomyosin-dependent process. Our data reveal that mechanisms controlling the establishment of the D quadrant differ fundamentally even among the monophyletic clitellate annelids. Thus, while the homologous spiral cleavage pattern is highly conserved in this clade, it has diverged significantly at the level of cell biological mechanisms. This combination of operational conservation and mechanistic divergence begins to explain how the spiral cleavage program has remained so refractory to change while, paradoxically, accommodating numerous modifications throughout evolution.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Developmental Biology - Volume 334, Issue 1, 1 October 2009, Pages 46–58
نویسندگان
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