The fushi tarazu zebra element is not required for Drosophila viability or fertility.

Expression of genes in precisely controlled spatiotemporal patterns is essential for embryonic development. Much of our understanding of mechanisms regulating gene expression comes from the study of cis-regulatory elements (CREs) that direct expression of reporter genes in transgenic organisms. This reporter-transgene approach identifies genomic regions sufficient to drive expression but fails to provide information about quantitative and qualitative contributions to endogenous expression, although such conclusions are often inferred. Here we evaluated the endogenous function of a classic Drosophila CRE, the fushi tarazu (ftz) zebra element. ftz is a pair-rule segmentation gene expressed in seven stripes during embryogenesis, necessary for formation of alternate body segments. Reporter transgenes identified the promoter-proximal zebra element as a major driver of the seven ftz stripes. We generated a precise genomic deletion of the zebra element (ftzΔZ) to assess its role in the context of native chromatin and neighboring CREs, expecting large decreases in ftz seven-stripe expression. However, significant reduction in expression was found for only one stripe, ftz stripe 4, expressed at ∼25% of wild type levels in ftzΔZ homozygotes. Defects in corresponding regions of ftzΔZ mutants suggest this level of expression borders the threshold required to promote morphological segmentation. Further, we established true-breeding lines of homozygous ftzΔZ flies, demonstrating that the body segments missing in the mutants are not required for viability or fertility. These results highlight the different types of conclusions drawn from different experimental designs and emphasize the importance of examining transcriptional regulatory mechanisms in the context of the native genomic environment.

Dynamic expression of Drosophila segmental cell surface-encoding genes and their pair-rule regulators.

Drosophila segmentation is regulated by a complex network of transcription factors that include products of the pair-rule genes (PRGs). PRGs are expressed in early embryos in the primorida of alternate segmental units, establishing the repeated, segmental body plan of the fly. Despite detailed analysis of the regulatory logic among segmentation genes, the relationship between these genes and the morphological formation of segments is still poorly understood, since regulation of transcription factor expression is not sufficient to explain how segments actually form and are maintained. Cell surface proteins containing Leucine rich repeats (LRR) play a variety of roles in development, and those expressed in segmental patterns likely impact segment morphogenesis. Here we explore the relationships between the PRG network and segmentally expressed LRR-encoding (sLRR) genes. We examined expression of Toll2, Toll6, Toll7, Toll8 and tartan (trn) in wild type or PRG mutant embryos. Expression of each sLRR-encoding gene is dynamic, but each has a unique register along the anterior-posterior axis. The registers for different sLRRs are off-set from one another resulting in a continually changing set of overlapping expression patterns among the sLRR-encoding genes themselves and between the sLRR-encoding genes and the PRGs. Accordingly, each sLRR-encoding gene is regulated by a unique combination of PRGs. These findings suggest that one role of the PRG network is to promote segmentation by establishing a cell surface code: each row of cells in the two-segment-wide primordia expresses a unique combination of sLRRs, thereby translating regulatory information from the PRGs to direct segment morphogenesis.

Effect of Cadence on Time Trial Performance in Recreational Female Cyclists.

Graham, PL, Zoeller, RF, Jacobs, PL, and Whitehurst, MA. Effect of cadence on time trial performance in recreational female cyclists. J Strength Cond Res 32(6): 1739-1744, 2018-The impact of pedaling cadence on cycling performance remains unresolved especially in female cyclists. The purpose of this study was to determine the effect of cadence on time trial (TT) performance in recreational female cyclists. Ten recreational female cyclists volunteered to participate in this study. Subjects performed 3 exercise sessions: 1 to assess peak oxygen uptake (V[Combining Dot Above]O2peak) and 2 TTs. Cadence was randomly ordered and fixed for each TT (60 or 100 rpm), whereas power output (PO) was freely adjusted by the participant, as tolerated. Time trial time, heart rate (HR), blood lactate, PO, V[Combining Dot Above]O2, and ratings of perceived exertion were measured throughout the TTs. The major finding of this study was the significantly faster (p = 0.001) TT time during the 60-rpm condition (34:23 ± 4:21) vs. the 100-rpm condition (37:34 ± 5:53). Also the 60-rpm TT resulted in significant differences for HR (155.9 ± 3.97 vs. 161.2 ± 5.20 b·min, p = 0.04), gross efficiency, (21.1 ± 0.37 vs. 17.7 ± 0.85%, p < 0.001), and PO (147 ± 7.06 vs. 129 ± 10.62 W, p = 0.003). Thus, a slower cycling cadence was associated with greater mechanical efficiency and PO, resulting in significantly better performance in a TT. These results suggest that recreational female cyclists may benefit from adopting a low cadence during an 8-km TT.

Longitudinal Changes in Body Composition by Dual-energy Radiograph Absorptiometry Among Perinatally HIV-infected and HIV-uninfected Youth: Increased Risk of Adiposity Among HIV-infected Female Youth.

BACKGROUND: Combination antiretroviral therapy has allowed youth with perinatal HIV infection (PHIV+) to live into adulthood, but many youth may experience metabolic and body composition changes that predispose to greater cardiovascular disease (CVD) risk. This longitudinal study evaluated changes in body composition measured by dual-energy radiograph absorptiometry (DXA) in a cohort of PHIV+ youth compared with HIV- controls over a 7-year period. METHODS: PHIV+ youth and HIV- controls were prospectively enrolled in a single-site study to assess nutrition and CVD risk. Anthropometrics and DXA scans were longitudinally obtained to assess percent body fat and regional fat distribution. Using general linear models, we analyzed differences in body composition and anthropometric measures by sex between PHIV+ youth and controls over time. RESULTS: Two hundred thirty-five participants (156 PHIV+ and 79 HIV- controls) with at least 1 DXA performed since study enrollment were included for analysis. During the study period, 471 DXAs were obtained in the PHIV+ group and 95 in HIV- controls. PHIV+ females demonstrated greater increase in weight and body mass index over time compared with HIV- females, and significant increases in total percent body fat [estimate = 1.212 (95% confidence interval: 0.837-1.587) percent per year; P < 0.001) and percent trunk fat [1.3818 (95% confidence interval: 0.922-1.84); P < 0.001] compared with HIV- females and PHIV+ males. CONCLUSIONS: PHIV+ females demonstrate an unfavorable change in fat redistribution and percent body fat over time that exceeds the pattern seen in PHIV+ males or HIV- females. Providers should have heightened awareness of body composition changes of PHIV+ females that may eventually lead to increased CVD risk.

The translation initiation factor eIF4E regulates the sex-specific expression of the master switch gene Sxl in Drosophila melanogaster.

In female fruit flies, Sex-lethal (Sxl) turns off the X chromosome dosage compensation system by a mechanism involving a combination of alternative splicing and translational repression of the male specific lethal-2 (msl-2) mRNA. A genetic screen identified the translation initiation factor eif4e as a gene that acts together with Sxl to repress expression of the Msl-2 protein. However, eif4e is not required for Sxl mediated repression of msl-2 mRNA translation. Instead, eif4e functions as a co-factor in Sxl-dependent female-specific alternative splicing of msl-2 and also Sxl pre-mRNAs. Like other factors required for Sxl regulation of splicing, eif4e shows maternal-effect female-lethal interactions with Sxl. This female lethality can be enhanced by mutations in other co-factors that promote female-specific splicing and is caused by a failure to properly activate the Sxl-positive autoregulatory feedback loop in early embryos. In this feedback loop Sxl proteins promote their own synthesis by directing the female-specific alternative splicing of Sxl-Pm pre-mRNAs. Analysis of pre-mRNA splicing when eif4e activity is compromised demonstrates that Sxl-dependent female-specific splicing of both Sxl-Pm and msl-2 pre-mRNAs requires eif4e activity. Consistent with a direct involvement in Sxl-dependent alternative splicing, eIF4E is associated with unspliced Sxl-Pm pre-mRNAs and is found in complexes that contain early acting splicing factors--the U1/U2 snRNP protein Sans-fils (Snf), the U1 snRNP protein U1-70k, U2AF38, U2AF50, and the Wilms' Tumor 1 Associated Protein Fl(2)d--that have been directly implicated in Sxl splicing regulation.