Studying roles of the kinetochore component Ndc80 in spindle assembly checkpoint

Accurate chromosome segregation relies on the kinetochore, a multiprotein structure, which assembles around the centromeric region of the chromosome. Proper kinetochore-microtubule attachment is critical for the segregation of sister chromatids toward the opposite poles during mitosis. The outer kinetochore, notably the KMN network (KNL-1 complex/Mis12 complex/Ndc80 complex), links chromosomes to the mitotic spindle, in which the Ndc80 protein is a primary microtubule-binding site. Any improper attachments are recognised by the spindle assembly checkpoint (SAC), a surveillance pathway, which blocks premature segregation of chromosomes by preventing anaphase onset. Incorrect kinetochore-microtubule attachments lead to SAC activation, which is coupled with localisation of its components (Mph1/MPS1, Mad1, Mad2, Mad3/BubR1, Bub1 and Bub3) to the kinetochores. However, the mechanisms by which SAC components other than Bub1 and Bub3 are recruited to the kinetochore remain largely elusive. In this study, I show isolation and characterisation of an ndc80 mutant (ndc80-AK01) in fission yeast. The ndc80-AK01 mutant contains a single point mutation within an uncharacterised linker/hairpin region that connects a calponin-homology domain and a coiled-coil domain. This mutant is hypersensitive to microtubule poisons with no apparent growth defects in the absence of drugs. Subsequent analysis indicates that ndc80-AK01 is defective in SAC signalling. Localisation studies of SAC components have shown the absence of GFP-tagged Ark1, Mph1, Bub1, Bub3, Mad3, Mad2 and Mad1 from kinetochores under mitotic arrest conditions. Genetic and cell biological data indicate that the Ndc80 linker region may act as a structural platform for kinetochore recruitment of Mph1, which is one of the most upstream SAC components. Intriguingly, artificial tethering of Mph1 to the kinetochore restores checkpoint signalling in the ndc80-AK01 mutant, further confirming the function of Ndc80 as a kinetochore platform for Mph1. These data have unveiled a hitherto unknown function of the Ndc80 linker region in the SAC

Genetics of Whole Plant Morphology and Architecture

Plant architectural features directly impact plant fitness and adaptation, and traits related to plant morphology and development represent important targets for crop breeding. Decades of mutagenesis research have provided a wealth of mutant resources, making barley (Hordeum vulgare L.) an interesting model for genetic dissection of grass morphology and architecture. Recent advances in genomics have propelled the identification of barley genes controlling different aspects of shoot and root development. In addition to gene discovery, it is important to understand the interplay between different developmental processes in order to support breeding of improved ideotypes for sustainable barley production under different climatic conditions. The purpose of the present chapter is to: (i) provide an overview of the morphology and development of shoot and root structures in barley; (ii) discuss novel insights into the genetic, molecular and hormonal mechanisms regulating root and shoot development and architecture; and (iii) highlight the genetic and physiological interactions among organs and traits with special focus on correlations between leaf and tiller development, flowering and tillering, as well as row-type and tillering

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the "immunome" and "microbiome". It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development