The literature on the mouse sperm morphology test and on other sperm tests in nonhuman mammals was reviewed (a) to evaluate the relationship of these tests to chemically induced spermatogenic dysfunction, germ-cell mutagenicity, and carcinogenicity, and (b) to make an interspecies comparison of responses to chemicals. A total of 71 papers were reviewed.
The mouse sperm morphology test was used to assess the effects of 154 of the 182 chemical agents covered. 4 other murine sperm tests were also used: the induction of acrosomal abnormalities (4 agents), reduction in sperm counts (6 agents), motility (5 agents), and F1 sperm morphology (7 agents). In addition, sperm tests for the spermatogenic effects of 35 agents were done in 9 nonmurine mammalian species; these included analyses for sperm count, motility, and morphology, using a large variety of study designs. For the mouse sperm morphology test, 41 agents were judged by the reviewing committee to be positive inducers of sperm-head shape abnormalities, 103 were negative, and 10 were inconclusive.
To evaluate the relationship between changes in sperm morphology and germ cell mutagenicity, the effects of 41 agents on mouse sperm shape were compared to available data from 3 different mammalian germ-cell mutational tests (specific locus, heritable translocation, and dominant lethal). The mouse sperm morphology test was found to be highly sensitive to germ-cell mutagens; 100% of the known mutagens were correctly identified as positives in the sperm morphology test. Data are insufficient at present to access the rate of false positives. Although it is biologically unclear why one might expect changes in sperm morphology to be related to carcinogenesis, we found that (a) a positive response in the mouse sperm morphology test is highly specific for carcinogenic potential (100% for the agents surveyed), but (b) overall, only 50% of carcinogens were positive in the test (i.e., sensitivity ⋍ 50%). Since many carcinogens do not produce abnormally shaped sperm even at lethal doses, negative findings with the sperm test cannot be used to classify agents as noncarcinogens. We conclude that the mouse sperm morphology test has potential use for identifying chemicals that induce spermatogenic dysfunction and perhaps heritable mutations. Positive test results may also be useful in assessing carcinogenic potential. Insufficient numbers of chemicals agents have been studied by the other sperm tests to permit similar comparisons.
A comparison of 25 chemicals tested with sperm counts, motility, and morphology in at least 2 species (including man, mouse and 9 other mammals) demonstrated good agreement in response among species. With further study, interspecies comparisons of chemically induced sperm changes may be useful for predicting and evaluating human effects.
Research highlight – Resident microbes in development: a gut feeling for Notch
Various aspects of animal development are influenced by the host's microbiota. For instance, zebrafish reared in a germ-free environment show abnormal cell fate allocation in the intestine, but whether this process is linked to Notch signalling was previously unclear. Now, Karen Guillemin, Judith Eisen and colleagues combine gnotobiotic and genetic manipulations to test this relationship.
Development at a glance – Cytokinin signaling in plant development
In this poster and accompanying article, Joseph J. Kieber and G. Eric Schaller summarise the current understanding of cytokinin metabolism, transport and signalling, and discuss how this phytohormone regulates changes in gene expression to mediate its pleiotropic effects.
Spotlight – An interview with Ykä Helariutta
You can actually ask questions that people have not asked before in systems that have not been used before
New Development Editor Ykä Helariutta heads groups working on vascular development in plants and trees at both the University of Helsinki and the University of Cambridge. He shares how his career in plant gene discovery and mapping was a natural evolution of his childhood interest in plant taxonomy, and the benefits of taking risks with non-model organisms.
preLights is live!
preLights, the community-led biology preprints highlight service hosted by The Company of Biologists, launched on February 20th. To find out more about preLights, read the Editorial by our Editor-in-Chief Olivier Pourquié and Executive Editor Katherine Brown.
On the Node: The people behind the papers
We meet Marina Matsumiya and Ryoichiro Kageyama of Kyoto University, and hear about their new stem cell-derived tool for studying the segmentation clock, recently published in Development.
Articles of interest in our sister journals
Maturation of neural stem cells and integration into hippocampal circuits – a functional study in an in situ model of cerebral ischemia
Olga Kopach, Oksana Rybachuk, Volodymyr Krotov, Vitalii Kyryk, Nana Voitenko, Tatyana Pivneva
J Cell Sci 2018 131: jcs210989 doi: 10.1242/jcs.210989
The developing Drosophila eye – a new model to study centriole reduction
Maria G. Riparbelli, Veronica Persico, Marco Gottardo, Giuliano Callaini
J Cell Sci 2018 131: jcs211441 doi: 10.1242/jcs.211441