Aims:  To evaluate the frequency of the aerolysin (aerA), cytotoxic enterotoxin (alt) and serine protease (ahp) genes in Aeromonas hydrophila isolates from different sources, and to determine the relationship between the presence of these genes and virulence of A. hydrophila in zebrafish. Methods and Results:  Aeromonas hydrophila isolates from clinical cases (n = 40), from healthy fish (n = 22) and from water environment (n = 21) were analysed with respect to the prevalence of aerA, alt and ahp genes by PCR assay. These virulence factors occur among clinical isolates as well as among isolates from healthy fish and water environment. The majority (97·6%) of the strains examined carried one or more virulence genes. The isolates were divided into seven genetic profiles on the basis of PCR result: aerA+alt+ahp+ (62·7%), aerA+alt+ahp− (13·3%), aerA+alt−ahp+ (10·8%), aerA−alt+ahp+ (4·8%), aerA−alt−ahp+ (3·6%), aerA+alt−ahp− (2·4%) and aerA−alt−ahp− (2·4%). A higher frequency of genetic group aerA+alt+ahp+ was determined in the isolates from diseased animals compared to those from healthy fish or water environments. Virulence properties of 26 representative strains belonging to the seven genetic profiles were further characterized. Results demonstrated that as the present of virulence genes increased, the proteolytic, haemolytic and cytotoxic activities of extracellular products also increased. And the 50% lethal doses (LD50s) of aerA+alt+ahp+ isolates (<105) in zebrafish were lower when compared with the strains expressing one or combinations of two virulence genes (>106). Conclusions:  Virulence properties of A. hydrophila correlated well with the presence of virulence genes tested. aerA+alt+ahp+ was more frequent virulence genotype in A. hydrophila isolates from clinical diseases than from healthy fish and water environment, and the aerA+alt+ahp+ isolates were more virulent to zebrafish compared to the other six genetic profiles. Significant and Impact of the Study:  The detection for aerA, alt and ahp can be used for virulence typing of A. hydrophila isolates.

Epithelial invagination is a fundamental module of morphogenesis that iteratively occurs to generate the architecture of many parts of a developing organism. By changing the physical properties such as the shape and/or position of a population of cells, invagination drives processes ranging from reconfiguring the entire body axis during gastrulation, to forming the primordia of the eyes, ears and multiple ducts and glands, during organogenesis. The epithelial bending required for invagination is achieved through a variety of mechanisms involving systems of cells. Here we provide an overview of the different mechanisms, some of which can work in combination, and outline the circumstances in which they apply.This article is part of the themed issue ‘Systems morphodynamics: understanding the development of tissue hardware’.

Chromosome segregation in mitosis is orchestrated by dynamic interaction between spindle microtubules and the kinetochore. Septin (SEPT) belongs to a conserved family of polymerizing GTPases localized to the metaphase spindle during mitosis. Previous study showed that SEPT2 depletion results in chromosome mis-segregation correlated with a loss of centromere-associated protein E (CENP-E) from the kinetochores of congressing chromosomes (1). However, it has remained elusive as to whether CENP-E physically interacts with SEPT and how this interaction orchestrates chromosome segregation in mitosis. Here we show that SEPT7 is required for a stable kinetochore localization of CENP-E in HeLa and MDCK cells. SEPT7 stabilizes the kinetochore association of CENP-E by directly interacting with its C-terminal domain. The region of SEPT7 binding to CENP-E was mapped to its C-terminal domain by glutathione S-transferase pull-down and yeast two-hybrid assays. Immunofluorescence study shows that SEPT7 filaments distribute along the mitotic spindle and terminate at the kinetochore marked by CENP-E. Remarkably, suppression of synthesis of SEPT7 by small interfering RNA abrogated the localization of CENP-E to the kinetochore and caused aberrant chromosome segregation. These mitotic defects and kinetochore localization of CENP-E can be successfully rescued by introducing exogenous GFP-SEPT7 into the SEPT7-depleted cells. These SEPT7-suppressed cells display reduced tension at kinetochores of bi-orientated chromosomes and activated mitotic spindle checkpoint marked by Mad2 and BubR1 labelings on these misaligned chromosomes. These findings reveal a key role for the SEPT7-CENP-E interaction in the distribution of CENP-E to the kinetochore and achieving chromosome alignment. We propose that SEPT7 forms a link between kinetochore distribution of CENP-E and the mitotic spindle checkpoint.Chromosome movements during mitosis are governed by the interaction of spindle microtubules with a specialized chromosome domain located within the centromere. This specialized region, called the kinetochore (2), is the site for spindle microtubule-centromere association. In addition to providing a physical link between chromosomes and spindle microtubules, the kinetochore plays an active role in chromosomal segregation through microtubule motors and spindle checkpoint sensors located at or near it (3). During mitosis, attaching, positioning, and bi-orientating, kinetochores with the spindle microtubules play essential roles in chromosome segregation and genomic stability.CENP-E 3 is a microtubule-based kinesin motor protein located on the outer kinetochore and is involved in a stable microtubule-kinetochore attachment (4). CENP-E participates in the chromosome movements from prometaphase to anaphase (5) by tethering the kinetochores to microtubule "plus" ends and moving toward the equator (3, 6), thereby helping mono-oriented chromosomes align at the metaphase plate before bi-orientation (7). A recent study showed that the mammalian septin network coop...

Wound healing is essential for survival. We took advantage of the Xenopus embryo, which exhibits remarkable capacities to repair wounds quickly and efficiently, to investigate the mechanisms responsible for wound healing. Previous work has shown that injury triggers a rapid calcium response, followed by the activation of Ras homolog (Rho) family guanosine triphosphatases (GTPases), which regulate the formation and contraction of an F-actin purse string around the wound margin. How these processes are coordinated following wounding remained unclear. Here we show that inositol-trisphosphate 3-kinase B (Itpkb) via its enzymatic product inositol 1,3,4,5-tetrakisphosphate (InsP 4 ) plays an essential role during wound healing by modulating the activity of Rho family GTPases and F-actin ring assembly. Furthermore, we show that Itpkb and InsP 4 modulate the speed of the calcium wave, which propagates from the site of injury into neighboring uninjured cells. Strikingly, both overexpression of itpkb and exogenous application of InsP 4 accelerate the speed of wound closure, a finding that has potential implications in our quest to find treatments that improve wound healing in patients with acute or chronic wounds.