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Background: Amyloid precursor protein (APP) is widely recognized for playing a central role in Alzheimer's disease pathogenesis. Although APP is expressed in several tissues outside the human central nervous system, the functions of APP and its family members in other tissues are still poorly understood. APP is involved in several biological functions which might be potentially important for male fertility, such as cell adhesion, cell motility, signaling, and apoptosis. Furthermore, APP superfamily members are known to be associated with fertility. Knowledge on the protein networks of APP in human testis and spermatozoa will shed light on the function of APP in the male reproductive system. Results: We performed a Yeast Two-Hybrid screen and a database search to study the interaction network of APP in human testis and sperm. To gain insights into the role of APP superfamily members in fertility, the study was extended to APP-like protein 2 (APLP2). We analyzed several topological properties of the APP interaction network and the biological and physiological properties of the proteins in the APP interaction network were also specified by gene ontologyand pathways analyses. We classified significant features related to the human male reproduction for the APP interacting proteins and identified modules of proteins with similar functional roles which may show cooperative behavior for male fertility. Conclusions: The present work provides the first report on the APP interactome in human testis. Our approach allowed the identification of novel interactions and recognition of key APP interacting proteins for male reproduction, particularly in sperm-oocyte interaction. [ABSTRACT FROM AUTHOR]

Mms19 encodes a cytosolic iron-sulphur assembly component. We found that Drosophila Mms19 is also essential for mitotic divisions and for the proliferation of diploid cells. Reduced Mms19 activity causes severe mitotic defects in spindle dynamics and chromosome segregation, and loss of zygotic Mms19 prevents the formation of imaginal discs. The lack of mitotic tissue in Mms19 P/P larvae can be rescued by overexpression of the Cdk-activating kinase (CAK) complex, an activator of mitotic Cdk1, suggesting that Mms19 functions in mitosis to allow CAK (Cdk7/Cyclin H/Mat1) to become fully active as a Cdk1-activating kinase. When bound to Xpd and TFIIH, the CAK subunit Cdk7 phosphorylates transcriptional targets and not cell cycle Cdks. In contrast, free CAK phosphorylates and activates Cdk1. Physical and genetic interaction studies between Mms19 and Xpd suggest that their interaction prevents Xpd from binding to the CAK complex. Xpd bound to Mms19 therefore frees CAK complexes, allowing them to phosphorylate Cdk1 and facilitating progression to metaphase. The structural basis for the competitive interaction with Xpd seems to be the binding of Mms19, core TFIIH and CAK to neighbouring or overlapping regions of Xpd., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

The basidiomycete fungus Ustilago maydis has emerged as a powerful model organism to study fundamental biological processes. U. maydis shares many important features with human cells but provides the technical advantages of yeast. Recently, U. maydis has also been used to investigate fundamental processes in peroxisome biology. Here, we present an efficient yeast recombination-based cloning method to construct and express fluorescent fusion proteins (or conditional mutant protein alleles) which target peroxisomes in the fungus U. maydis. In vivo analysis is pivotal for understanding the underlying mechanisms of organelle motility. We focus on the in vivo labeling of peroxisomes in U. maydis and present approaches to analyze peroxisomal motility.

We have previously characterized an EMS-induced allele of the bubR1 gene (bubR1(D1326N)) that separates the two functions of BubR1, causing meiotic nondisjunction but retaining spindle assembly checkpoint activity during somatic cell division in Drosophila melanogaster. Using this allele, we demonstrate that bubR1 meiotic nondisjunction is dosage sensitive, occurs for both exchange and nonexchange homologous chromosomes, and is associated with decreased maintenance of sister chromatid cohesion and of the synaptonemal complex during prophase I progression. We took advantage of these features to perform a genetic screen designed to identify third chromosome deficiencies having a dominant effect on bubR1(D1326N)/bubR1(rev1) meiotic phenotypes. We tested 65 deficiencies covering 60% of the third chromosome euchromatin. Among them, we characterized 24 deficiencies having a dominant effect on bubR1(D1326N)/bubR1(rev1) meiotic phenotypes that we classified in two groups: (1) suppressor of nondisjunction and (2) enhancer of nondisjunction. Among these 24 deficiencies, our results show that deficiencies uncovering the polo locus act as suppressor of bubR1 nondisjunction by delaying meiotic prophase I progression and restoring chiasmata formation as observed by the loading of the condensin subunit SMC2. Furthermore, we identified two deficiencies inducing a lethal phenotype during embryonic development and thus affecting BubR1 kinase activity in somatic cells and one deficiency causing female sterility. Overall, our genetic screening strategy proved to be highly sensitive for the identification of modifiers of BubR1 kinase activity in both meiosis and mitosis.