Saccharomyces cerevisiae Mer2, Mei4 and Rec114 form a complex required for meiotic double-strand break formation

In budding yeast, at least 10 proteins are required for formation of the double-strand breaks (DSBs) that initiate meiotic recombination. Spo11 is the enzyme responsible for cleaving DNA and is found in a complex that also contains Ski8, Rec102, and Rec104. The Mre11/Rad50/Xrs2 complex is required for both DSB formation and DSB processing. In this article we investigate the functions of the remaining three proteins--Mer2, Mei4, and Rec114--with particular emphasis on Mer2. The Mer2 protein is present in vegetative cells, but it increases in abundance and becomes phosphorylated specifically during meiotic prophase. Mer2 localizes to distinct foci on meiotic chromosomes, with foci maximally abundant prior to the formation of synaptonemal complex. If DSB formation is blocked (e.g., by a spo11 mutation), dephosphorylation of Mer2 and its dissociation from chromosomes are delayed. We have also found that the Mei4 and Rec114 proteins localize to foci on chromosomes and these foci partially colocalize with each other and with Mer2. Furthermore, the three proteins co-immunoprecipitate. Mer2 does not show significant colocalization with Mre11 or Rec102 and Mer2 does not co-immunoprecipitate with Rec102. We propose that Mer2, Mei4, and Rec114 form a distinct complex required for DSB formation.     

Where Will the Baby Sleep? Attitudes and Practices of New and Experienced Parents Regarding Cosleeping with Their Newborn Infants

An evolutionary perspective on human infant sleep physiology suggests that parent-infant cosleeping, practiced under safe conditions, might be beneficial to both mothers and infants. However, cosleeping is not part of mainstream parenting ideology in the United States or the United Kingdom, and little evidence is available to indicate whether, and under what circumstances, parents sleep with their newborn infants. We present data from an anthropological investigation into the practices and attitudes of new and experienced parents of newborn infants regarding parent-infant sleeping arrangements in a community in the northeast of England. Despite not having contemplated cosleeping prior to the birth, new parents in our sample found it to be a convenient nighttime caregiving strategy, and one which was practiced regularly. Infants slept with both their parents, some being habitual all-night cosleepers, but commonly beginning the night in a cnb and sleeping with their parents for several hours following the early morning feed, [infant sleep, newborn, cosleeping, new parents]     

Using Fiction to Assess Mental State Understanding: A New Task for Assessing Theory of Mind in Adults

Social functioning depends on the ability to attribute and reason about the mental states of others – an ability known as theory of mind (ToM). Research in this field is limited by the use of tasks in which ceiling effects are ubiquitous, rendering them insensitive to individual differences in ToM ability and instances of subtle ToM impairment. Here, we present data from a new ToM task – the Short Story Task (SST) - intended to improve upon many aspects of existing ToM measures. More specifically, the SST was designed to: (a) assess the full range of individual differences in ToM ability without suffering from ceiling effects; (b) incorporate a range of mental states of differing complexity, including epistemic states, affective states, and intentions to be inferred from a first- and second-order level; (c) use ToM stimuli representative of real-world social interactions; (d) require participants to utilize social context when making mental state inferences; (e) exhibit adequate psychometric properties; and (f) be quick and easy to administer and score. In the task, participants read a short story and were asked questions that assessed explicit mental state reasoning, spontaneous mental state inference, and comprehension of the non-mental aspects of the story. Responses were scored according to a rubric that assigned greater points for accurate mental state attributions that included multiple characters’ mental states. Results demonstrate that the SST is sensitive to variation in ToM ability, can be accurately scored by multiple raters, and exhibits concurrent validity with other social cognitive tasks. The results support the effectiveness of this new measure of ToM in the study of social cognition. The findings are also consistent with studies demonstrating significant relationships among narrative transportation, ToM, and the reading of fiction. Together, the data indicate that reading fiction may be an avenue for improving ToM ability.     

Study of the mitotic and meiotic chromosomes of sotol (<i>Dasylirion cedrosanum</i> Trel.)

The genus Dasylirion is a group of plants typically present in the Chihuahuan Desert, perennial, with a dioecious sexual behavior and commonly called sotoles. This genus has been little studied from the biological point of view, and the bases of its reproductive response remain unknown. In this work we studied the chromosome number and meiotic response of Dasylirion cedrosanum in the county of Saltillo, Coahuila, located at the North East of Mexico. For the preparation of mitotic chromosomes, we used a technique based on enzymatic treatment with pectolyase and cellulase, as well as staining with acetocarmin dye. For the study of meiosis, male flower buds were collected, fixed and stained for analysis with the same dye. As a result, the gametic (n = x = 19) and somatic chromosome (2n = 38) numbers of D. cedrosanum are reported for the first time, being consistent with previous findings in other Dasylirion species, which points to a constant ploidy level across the genus. Variation was observed in the morphology and size of the somatic chromosomes, with types ranging from submetacentric to subtelocentric, and sizes oscillating in a range of 4.43 µm, with an average total length of 112.38 µm for the diploid chromosome complement. This shows that the chromosome complement of D. cedrosanom would belong to a 3B classification of Stebins, with a medium variation between chromosome lengths and low chromosome asymmetry. This variation indicates the feasibility of constructing a chromosome ideotype for this species. The meiotic chromosome pairing showed a chromosome behavior consistent with a disomic inheritance characteristic of a diploid species, with prevalence of ring and chain bivalents, typically without pairing abnormalities. Bivalent configurations in all cases were symmetrical.The normal and symmetrical meiotic pairing indicates a balanced production of gametes, and suggests the absence of heteromorphic sex determination.