Executionary pathway for apoptosis:lessons from mutant mice

Apoptosis or programmed cell death (PCD) is an evolutionarily conserved cellular process that is essential for normal development and homeostasis of multicellular organisms. Defects in the apoptosis signaling result in many diseases including autoimmune diseases and cancer. The apoptosis signaling pathway was first described genetically in the nematode Caenorhabditis elegans which serves as a framework for the more complex apoptotic pathways that exist in mammals. In this review, we will discuss the apoptotic pathways that are emerging in mammals as elucidated by studies of gene-targeted mutant mice.

An atypical ubiquitin ligase at the heart of neural development and programmed axon degeneration

The degeneration of nerve fibres following injury was first described by Augustus Waller over 170 years ago.Initially assumed to be a passive process,it is now evident that axons respond to insult via regulated cellular signaling events resulting in their programmed degeneration.Pro-survival and prodegenerative factors have been identified and their regulato ry mechanisms are beginning to emerge.The ubiquitin system has been implicated in the pro-degenerative process and a key component is the ubiquitin E3 ligase MYCBP2(also known as PHR1).Ubiquitin E3 ligases are tasked with the transfer of the small protein modifier ubiquitin to substrates and consist of hundreds of members.They can be classified as single subunit systems or as multi-subunit complexes.Their catalytic domains can also be assigned to three general architectures.Hints that MYCBP2 might not conform to these established formats came to light and it is now clear from biochemical and structural studies that MYCBP2 is indeed an outlier in terms of its modus operandi.Furthermore,the unconventional way in which MYCBP2 transfe rs ubiquitin to substrates has been linked to neurodevelopmental and pro-degenerative function.Herein,we will summarize these research developments relating to the unusual features of MYCBP2 and postulate therapeutic strategies that prevent Walle rian degeneration.These have exciting potential for providing relief from pathological neuropathies and neurodegenerative diseases.

3ermline Development and Fertilization Vlechanisms in Maize

Maize is the most important agricultural crop used for food, feed, and biofuel as well as a raw material for industrial products such as packaging material. To increase yield and to overcome hybridization barriers, studies of maize gamete development, the pollen tube journey, and fertilization mechanisms were initiated more than a century ago. In this review, we summarize and discuss our current understanding of the regulatory components for germline development including sporogenesis and gametogenesis, the pro- gamic phase of pollen germination and pollen tube growth and guidance, as well as fertilization mecha- nisms consisting of pollen tube arrival and reception, sperm cell release, fusion with the female gametes, and egg cell activation. Mechanisms of asexual seed development are not considered here. While only a few molecular players involved in these processes have been described to date and the underlying mech- anisms are far from being understood, maize now represents a spearhead of reproductive research for all grass species. Recent development of essentially improved transformation and gene-editing systems may boost research in this area in the near future.