Component of the LINC (LInker of Nucleoskeleton and Cytoskeleton) complex involved in the connection between the nuclear lamina and the cytoskeleton (By similarity). Plays a role in the nuclear positioning and links the nucleus to the microtubule organizing center (MTOC) (PubMed:10556085, PubMed:22927463, PubMed:15579692). Collaborates with Klar to promote even spacing of the myonuclei at the periphery of striated muscle fibers by mediating a tight association between a nuclear ring structure of Msp300 and the plus ends of a unique astral microtubule (MT) network (PubMed:22927463). Core component of LINC complexes which are composed of inner nuclear membrane SUN domain-containing proteins coupled to outer nuclear membrane KASH domain-containing nesprins (By similarity). Interacts with kud (PubMed:28716842). Interacts with Msp300; this interaction allows the anchoring of Msp300 nuclear ring structure to the nuclear envelope (PubMed:22927463). Associated with microtubules, both apical to the nucleus and also at the basal-most area of the eye disk (PubMed:15579692, PubMed:18820457, PubMed:14617811). Koi is required for perinuclear localization of Klar (PubMed:18820457). Nuclear envelope localization requires nuclear lam (PubMed:14617811). Expressed ubiquitously in the eye disk, but at much higher levels posterior to the morphogenetic furrow (PubMed:18820457). Expressed in R-cells and also in non-neural cone cells (PubMed:18820457). The KASH domain mediates localization to the nuclear membrane (PubMed:15579692). Msp300 and Klar KASH domains cooperate to mediate the connection between a nuclear ring structure of Msp300 and the plus ends of a unique astral microtubule (MT) network (PubMed:22927463). Homozygous mutant flies are viable and fertile but have eye defects; photoreceptor nuclei fail to migrate apically as they are specified, resulting in aberrantly shaped photoreceptors in adult eyes (PubMed:28716842). In larval mutants eye disks, both the R-cell and cone cell nuclei are positioned randomly within the apical/basal axis (PubMed:18820457). Belongs to the nesprin family.