Areas Of Programmed Cell Death Research Articles

In vivo detection of programmed cell death during mouse heart development

Despite the great progress on the cell biology of programmed cell death (PCD), its incidence and exact time course during embryonic and particular heart development are still unclear. This is also due to the lack of models enabling to directly identify and monitor PCD cells at different time points in vivo. Herein we report generation of transgenic murine embryonic stem cell and mouse models expressing secreted Annexin V-YFP under control of the CAG promoter. This enables to visualize and quantify PCD in vitro and in vivo during embryonic development. At early embryonic stages we found Annexin V-YFP+ fluorescent cells in known areas of PCD, such as the otic ring and at the site of neural tube closing, underscoring its specificity for detection of PCD. We have focused our detailed analysis primarily on PCD in the embryonic heart for a better understanding of its role during development. Our findings reveal that PCD peaks at early stages of cardiogenesis (E9.5–E13.5) and strongly decreases thereafter. Moreover, the PCD cells in the heart are predominantly cardiomyocytes, and an unexpected area of prominent cardiac PCD are the ventricular trabeculae (E9.5–E14.5). Thus, the sA5-YFP mouse line provides novel insight into the incidence and relevance of cardiac PCD during embryonic development ex- and in vivo.

Interactions between FGFs and BMPs in the control of programmed cell death in the developing limb

Programmed cell death (PCD) has a major role in vertebrate limb morphogenesis. In the developing chick embryo four areas of PCD, the anterior necrotic zone (ANZ), the posterior necrotic zone (PNZ), the opaque patch (OP) and the interdigital necrotic zones (INZ) are responsible for sculpturing the shape of the limb. There is abundant evidence showing that BMPs are responsible for triggering apoptosis in the limb mesoderm (Macias et al., 1997). However, BMPs are at the same time the signals acounting for chondrogenesis (Zou et al., 1997; Pizette and Niswander, 2000). Local application of BMPs into the undifferentiated limb mesoderm causes apoptosis (Fig. 1A). However, the same treatment applied into the prechondrogenic mesenchyme results in massive chondrogenesis (Fig. 1 B,C). Thus, the stage of differentiation of the mesodermal target tissue appears to have a major influence between the two opposite effects of BMPs. FGFs are the signals responsible for maintaining the limb mesoderm in an undifferentiated and proliferating state (Martin,

Sequential changes of programmed cell death in developing fetal mouse limbs and its possible roles in limb morphogenesis.

Apoptotic cell death in the developing limb of mouse fetuses was examined sequentially on days 11-15 of gestation by means of Nile blue (NB) sulfate staining with special reference to its relation to limb morphogenesis. With some exceptions, programmed cell death (PCD) in the hand and foot was observed in the mesenchyme but not in the surface ectoderm. We found that during digital formation PCD begins at the proximal portion of the interdigital mesenchyme and subsequently expands distally. Therefore, the initial PCD that occurs in the interdigital zones may determine the proximal ends of digital separation and also contribute to the demarcation between the palm (sole) and digits (toes). During digital separation, the areas of PCD in the interdigital zones were found to become larger and expand distally on day 13, which may be necessary for the separation of digits and for determining the interdigital area to disappear. PCD in presumptive phalangeal joints was also found to proceed from proximal to more distal joints. The PCD in presumptive joints may be required for the separation of phalanges and metacarpal (metatarsal) bones and for the formation of joint cavities. In addition, intense PCD was observed in the radial (tibial) and ulnar (fibular) margins of the hand and foot plates for 4-5 days. Such PCD at marginal areas seems to prevent the formation of supernumerary digits (preaxial and postaxial polydactyly) and other digital malformations. Therefore, the timing when PCD commences and ends, the sites where PCD occurs, and the intensity, duration, and proximo-distal progress of PCD appear to be genetically determined, and the elimination of unnecessary cells by PCD may be essential for normal limb morphogenesis. The present findings also suggest that the normal progress of PCD in the hand and foot plates of rodent fetuses may prevent the formation of some limb malformations such as webbing fusion of digits, polydactyly, or cleft hand/foot.