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Ciona follicle cells

Posted by anoic on 30 Jan 2009 at 10:34 GMT

The paper suffers from a basic and unnoticed error in the analysis of the observations available for at least twenty five years on the nature, development and function of the follicle cells in Ciona as in other ascidians (Burighel P. & Cloney R.A. 1997. In Microscopic Anatomy of Invertebrates. pp. 221-347; Jeffery 1980. J. Exp. Zool. 212:279-289; Fuke 1983. Roux's Arch. Dev. Biol. 192:347-352; Hoshi et al. 1981. Dev. Biol. 86:117-121: Hice & Moody 1988. Dev. Biol. 127:408-420 ; Marino et al. 1999. PNAS 96:9633-963; Lambert & Lambert 1978. Science 200:64-65; Lambert et al. 1997. Mol. Reprod. Dev. 48:137-143; Cotelli et al.Roux's Arch. Develop. Biol. 1981. 190: 252). If not spoiling the whole paper it weakens at least some of the results reported. This misreading lead first of all to the wrong identification of “outer and inner follicle cells”: these two cell types are present, as clearly shown also in the paper by Sugino et al., only during oogenesis and the so called inner follicle cells are the only ones that surround the oocyte once it is released into the oviduct. There was then an absolutely arbitrary interpretation of the light microscopy and TEM images: the “nuclei localized at the tip of the follicular extensions” are not nuclei, but the refringent bodies described also more recently by Byrd and Lambert (Mechanism of the block to hybridization and selfing between the sympatric ascidians Ciona intestinalis and Ciona savignyi, Mol Reprod Dev. 2000 56:541).

RE: Ciona follicle cells

stbaghdi replied to anoic on 18 Feb 2009 at 13:21 GMT

We would like to answer to this comment on several levels.
1. We were well aware of the literature quoted in the comment. We apologize for not having cited these relevant papers, but the purpose of our study was much different, and the proposed role of apoptotic master cell given to inner follicle cells do not exclude all previously reported functions for these cells.
2. Some of the quoted papers are far from being conclusive on the aspects cited in the comment, namely: the Sugino’s paper (J. Exp. Zool. 242:205-214, 1987) does not formally demonstrate that… “the so-called inner follicle cells are the only ones that surround the oocyte once it is released into the oviduct.” Moreover, Fig. 13 of Sugino’s paper supports evidence for the existence of a close interconnection between outer and inner follicle cells; the Byrd & Lambert paper (Mol Reprod. Dev 55:109-116, 2000) lacks experimental evidence that the refringent body is not of nuclear nature. On the contrary, our own experiment indeed points that a specific marker of DNA fragmentation actually labels this structure (fig 1 & 4 of the present paper).
3. Anyway, if this TUNEL-positive structures were not of nuclear origin, and if the floating follicular extensions were uniquely made of inner follicular cells, then the only important message of our paper would be drastically strengthened, i.e. inner follicular cells, through their geometrical positioning, behave as apoptotic master cells that controls the life/death status of test cells. Then, the follicular model in Ciona would be worth to be compared with the cavitation event observed in mammals where a unique epithelial monolayer controls the destiny of inner cellular mass through an extracellular matrix.