Teflon promotes chromosomal recruitment of homolog conjunction proteins during Drosophila male meiosis.

Meiosis in males of higher dipterans is achiasmate. In their spermatocytes, pairing of homologs into bivalent chromosomes does not include synaptonemal complex and crossover formation. While crossovers preserve homolog conjunction until anaphase I during canonical meiosis, an alternative system is used in dipteran males. Mutant screening in Drosophila melanogaster has identified teflon (tef) as being required specifically for alternative homolog conjunction (AHC) of autosomal bivalents. The additional known AHC genes, snm, uno and mnm, are needed for the conjunction of autosomal homologs and of sex chromosomes. Here, we have analyzed the pattern of TEF protein expression. TEF is present in early spermatocytes but cannot be detected on bivalents at the onset of the first meiotic division, in contrast to SNM, UNO and MNM (SUM). TEF binds to polytene chromosomes in larval salivary glands, recruits MNM by direct interaction and thereby, indirectly, also SNM and UNO. However, chromosomal SUM association is not entirely dependent on TEF, and residual autosome conjunction occurs in tef null mutant spermatocytes. The higher tef requirement for autosomal conjunction is likely linked to the quantitative difference in the amount of SUM protein that provides conjunction of autosomes and sex chromosomes, respectively. During normal meiosis, SUM proteins are far more abundant on sex chromosomes compared to autosomes. Beyond promoting SUM recruitment, TEF has a stabilizing effect on SUM proteins. Increased SUM causes excess conjunction and consequential chromosome missegregation during meiosis I after co-overexpression. Similarly, expression of SUM without TEF, and even more potently with TEF, interferes with chromosome segregation during anaphase of mitotic divisions in somatic cells, suggesting that the known AHC proteins are sufficient for establishment of ectopic chromosome conjunction. Overall, our findings suggest that TEF promotes alternative homolog conjunction during male meiosis without being part of the final physical linkage between chromosomes.

Homologous chromosomes are stably conjoined for Drosophila male meiosis I by SUM, a multimerized protein assembly with modules for DNA-binding and for separase-mediated dissociation co-opted from cohesin.

For meiosis I, homologous chromosomes must be paired into bivalents. Maintenance of homolog conjunction in bivalents until anaphase I depends on crossovers in canonical meiosis. However, instead of crossovers, an alternative system achieves homolog conjunction during the achiasmate male meiosis of Drosophila melanogaster. The proteins SNM, UNO and MNM are likely constituents of a physical linkage that conjoins homologs in D. melanogaster spermatocytes. Here, we report that SNM binds tightly to the C-terminal region of UNO. This interaction is homologous to that of the cohesin subunits stromalin/Scc3/STAG and α-kleisin, as revealed by sequence similarities, structure modeling and cross-link mass spectrometry. Importantly, purified SU_C, the heterodimeric complex of SNM and the C-terminal region of UNO, displayed DNA-binding in vitro. DNA-binding was severely impaired by mutational elimination of positively charged residues from the C-terminal helix of UNO. Phenotypic analyses in flies fully confirmed the physiological relevance of this basic helix for chromosome-binding and homolog conjunction during male meiosis. Beyond DNA, SU_C also bound MNM, one of many isoforms expressed from the complex mod(mdg4) locus. This binding of MNM to SU_C was mediated by the MNM-specific C-terminal region, while the purified N-terminal part common to all Mod(mdg4) isoforms multimerized into hexamers in vitro. Similarly, the UNO N-terminal domain formed tetramers in vitro. Thus, we suggest that multimerization confers to SUM, the assemblies composed of SNM, UNO and MNM, the capacity to conjoin homologous chromosomes stably by the resultant multivalent DNA-binding. Moreover, to permit homolog separation during anaphase I, SUM is dissociated by separase, since UNO, the α-kleisin-related protein, includes a separase cleavage site. In support of this proposal, we demonstrate that UNO cleavage by tobacco etch virus protease is sufficient to release homolog conjunction in vivo after mutational exchange of the separase cleavage site with that of the bio-orthogonal protease.

Chromosome separation during Drosophila male meiosis I requires separase-mediated cleavage of the homolog conjunction protein UNO.

Regular chromosome segregation during the first meiotic division requires prior pairing of homologous chromosomes into bivalents. During canonical meiosis, linkage between homologous chromosomes is maintained until late metaphase I by chiasmata resulting from meiotic recombination in combination with distal sister chromatid cohesion. Separase-mediated elimination of cohesin from chromosome arms at the end of metaphase I permits terminalization of chiasmata and homolog segregation to opposite spindle poles during anaphase I. Interestingly, separase is also required for bivalent splitting during meiosis I in Drosophila males, where homologs are conjoined by an alternative mechanism independent of meiotic recombination and cohesin. Here we report the identification of a novel alternative homolog conjunction protein encoded by the previously uncharacterized gene univalents only (uno). The univalents that are present in uno null mutants at the start of meiosis I, instead of normal bivalents, are segregated randomly. In wild type, UNO protein is detected in dots associated with bivalent chromosomes and most abundantly at the localized pairing site of the sex chromosomes. UNO is cleaved by separase. Expression of a mutant UNO version with a non-functional separase cleavage site restores homolog conjunction in a uno null background. However, separation of bivalents during meiosis I is completely abrogated by this non-cleavable UNO version. Therefore, we propose that homolog separation during Drosophila male meiosis I is triggered by separase-mediated cleavage of UNO.

MNM and SNM maintain but do not establish achiasmate homolog conjunction during Drosophila male meiosis.

The first meiotic division reduces genome ploidy. This requires pairing of homologous chromosomes into bivalents that can be bi-oriented within the spindle during prometaphase I. Thereafter, pairing is abolished during late metaphase I, and univalents are segregated apart onto opposite spindle poles during anaphase I. In contrast to canonical meiosis, homologous chromosome pairing does not include the formation of a synaptonemal complex and of cross-overs in spermatocytes of Drosophila melanogaster. The alternative pairing mode in these cells depends on mnm and snm. These genes are required exclusively in spermatocytes specifically for successful conjunction of chromosomes into bivalents. Available evidence suggests that MNM and SNM might be part of a physical linkage that directly conjoins chromosomes. Here this notion was analyzed further. Temporal variation in delivery of mnm and snm function was realized by combining various transgenes with null mutant backgrounds. The observed phenotypic consequences provide strong evidence that MNM and SNM contribute directly to chromosome linkage. Premature elimination of these proteins results in precocious bivalent splitting. Delayed provision results in partial conjunction defects that are more pronounced in autosomal bivalents compared to the sex chromosome bivalent. Overall, our findings suggest that MNM and SNM cannot re-establish pairing of chromosomes into bivalents if provided after a chromosome-specific time point of no return. When delivered before this time point, they fortify preformed linkages in order to preclude premature bivalent splitting by the disruptive forces that drive chromosome territory formation during spermatocyte maturation and chromosome condensation during entry into meiosis I.

Losing Ground: Racial Disparities in Medical Debt and Home Foreclosure in the Deep South.

Medical debt is a persistent problem in the United States. This study examined the role of medical debt in relation to home foreclosure in a Deep South county with high rates of poverty, health disparities, and a racial gap in homeownership. Statistical analysis and geographic information systems mapping of municipal court records for 890 foreclosees indicated disproportionately high rates of medical debt among African Americans who lived in racially distinct neighborhoods. Both nonmedical and medical debt judgments were more numerous among African Americans than among whites; foreclosees in both groups had a higher medical debt burden compared with nonforeclosees. These results help to explain medical debt as a driver of foreclosure and racial disparities in homeownership.

Urban-rural differentials: a spatial analysis of Alabama students' recent alcohol use and marijuana use.

BACKGROUND AND OBJECTIVES: This study of Alabama public school students sought urban-rural differences in social and spatial mechanisms connecting structural factors to recent use of alcohol and marijuana. METHODS: Its dataset comprised a state-sponsored 2002 need-assessment survey of Alabama students; Alabama education department data; U. S. Census data; and alcohol-outlet locations listed by Alabama's Alcoholic Beverage Control Board. It measured structural-disadvantage factors (population disadvantages, community instability, alcohol-outlet density), social-organization factors (protective role of community, protective role of school), and recent-use factors. Using Geographic Information Systems (GIS), it generated maps of school catchment areas (SCAs)-the units of analysis for the study-that outline spatial patterns (across areas deemed urban or rural) of students' recent use of alcohol and marijuana. RESULTS: In the final sample of 370 SCAs, significant urban-versus-rural differences were observed for certain structural factors and in how these factors were associated with substance use. These differences aside, spatial analysis weighing the SCAs' particular geographic characteristics suggested location's importance, showing that a school playing a strong protective role significantly reduced not just its own students' recent substance use, but that of students in neighboring SCAs as well. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE: The findings show students' recent use of alcohol and marijuana are associated with characteristics of the environment. (Am J Addict 2013; 22:188-196).

A spatial analysis of student binge drinking, alcohol-outlet density, and social disadvantages.

BACKGROUND AND OBJECTIVES: This paper examined whether and how student binge drinking at the individual level was influenced by population disadvantages, community instability, alcohol-outlet density, and protective factors generated by community and school. METHODS: We used a dataset collected in 2002 by the Alabama Department of Mental Health, with additional materials generated by the 2000 Census and from the Alabama State Department of Education. School-catchments were employed as geographic units of analysis. The final sample comprised 78,138 public-school students in grades 6-12 who attended schools located in the 566 school-catchments. RESULTS: We hypothesized the presence of spatial processes that, once identified, would enhance understanding of student binge drinking. Our results confirmed that student binge drinking in a focal area was affected by that area's structural factors and also by individual-level risk and protective factors. The results did not support the hypothesized impact of surrounding areas' characteristics on student binge drinking in the focal area. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE: The results of our study clearly indicate that both environment-based factors and individual-level risk and protective factors are important in explaining student binge drinking in Alabama.

Sharecropper's Tuberculosis: Pathologies of Power in a Fatal Outbreak.

Tuberculosis Bacilli (TB) is a global scourge that affects poor people and regions. Drawing on Farmer's (2003) pathologies of power, and a case study approach, we examine the sociostructural landscape of a fatal outbreak of Sharecropper's TB among African Americans in rural Alabama. In a mixed-method qualitative approach involving oral history, surveys, interviews and documentary analysis, we identified three pathologies that contribute to TB susceptibility: corporate power, land wealth, and structural racism. While medicine can cure non-resistant forms of TB, control of future outbreaks will depend upon a social "cure" such as addressing structural inequality and building community trust in the health system.

Tomorrow's transcription tools: what new technology means for healthcare.

The year is 2006, and there are just a few hundred medical transcriptionists (MTs) still transcribing reports, serving only those older physicians who haven't changed with the times--and the times have definitely changed. Physicians have finally recognized the power of electronic health records (EHRs) as well as the fact that this power is realized only if they input clinical data directly into the EHR. The vast majority of physicians are using empirically refined templates, pick lists, and other methods of structured, codified input through the evolved progeny of today's Palm PCs, Pocket PCs, and Tablet PCs. Input methods include touch-screen, speech recognition, handwriting recognition, and perhaps other technology not yet invented. There are no longer any delays or expenses resulting from transcription. Plus healthcare organizations enjoy numerous benefits derived from analyzing codified clinical data. But this is only one vision. Another vision of 2006 incorporates an unavoidable reality: many physicians strongly resist directly inputting clinical data. They believe it slows them down, which outweighs the potentials overall healthcare benefits. Additionally, these physicians believe that structured input of patient information limits the freedom of expression afforded by free text. And frankly, these physicians don't put much stock in the value of clinical practive analysis. So transcription continues. In fact, it expands dramatically. Due to regulatory controls and other pressures, more providers dictate more clinical notes than ever. The need for MTs explodes. In 2006, there are half a million MTs required to convert voice dictations into text, more than double today's number.