SummaryWe have generated a transgenic mouse line, Tg(Stra8-cre)1Reb (Stra8-cre), which expresses improved Cre recombinase under the control of a 1.4 Kb promoter region of the germ cell-specific stimulated by retinoic acid gene 8 (Stra8). cre is expressed only in males beginning at postnatal day (P)3 in early-stage spermatogonia, and is detected through pre-leptotene-stage spermatocytes. To further define when cre becomes active, we crossed Stra8-cre males with Tg(ACTB-Bgeo/ GFP)21Lbe (Z/EG) reporter females and compared the expression of Enhanced Green Fluorescent Protein (EGFP) with the protein encoded by the zinc finger and BTB domain containing 16 (Zbtb16) gene, PLZF -a marker for undifferentiated spermatogonia. Co-expression of EGFP is observed in the majority of PLZF+ cells. We also tested recombination efficiency by mating Stra8-cre;Z/EG males and females with wild-type mice and examining EGFP expression in the offspring. Recombination is detected in >95% of Z/EG+ pups born to Stra8-cre;Z/EG fathers but in none of the offspring born to transgenic mothers, a verification that cre is not functional in females. The postnatal, premeiotic, male germ cell-specific activity of Stra8-cre makes this mouse line a unique resource to study testicular germ cell development. KeywordsCre recombinase; Stra8 promoter; spermatogonia; spermatocytes; Z/EG These experiments were initiated to produce a transgenic mouse line that expresses cre in undifferentiated spermatogonia. To date, the use of cre-mediated recombination to inactivate genes in developing germ cells at specific stages has been limited by the restricted expression patterns of available cre drivers. Recombination in primordial germ cells is possible using the alkaline phosphatase, liver/bone/kidney Alpl tm1(cre)Nagy mouse line (Lomeli et al., 2000). However, significant developmental events occur between the onset of cre at embryonic day (E)9.5 and the appearance of spermatogonia in the postnatal testis. Additional cre activity is detected in the placenta, intestine, and neural tube. Excision of floxed DNA in primary spermatocytes and elongating spermatids is achievable using synaptonemal complex protein 1 Tg(Sycp1-cre)4Min (Vidal et al., 1998) and protamine 1 Tg(Prm-cre)58Og (O'Gorman et al., 1997), respectively, but the temporal expression of these transgenes is too late to be of use in undifferentiated spermatogonia. Meanwhile, the expression of cre driven by the growth differentiation factor 9 (Gdf9) and zona pellucida 3 (Lan et al., 2004;Lewandoski et al., 1997).We therefore selected the promoter of the premeiotic male and female germ cell-specific gene Stra8 to drive expression of improved Cre recombinase. Endogenous Stra8 is first expressed in ovarian germ cells at E12.5 and continues until E16.5, while in males it is first transcribed in early-stage spermatogonia in the postnatal testis and persists in premeiotic germ cells throughout adulthood (Menke et al., 2003;Oulad-Abdelghani et al., 1996). A 1.4 Kb Stra8 promoter fragment was recently fused to EGF...
VegT is a T-box transcription factor whose mRNA is synthesized during oogenesis and localized in the vegetal hemisphere of the egg and early embryo. We show that maternally expressed VegT controls the pattern of primary germ layer specification in Xenopus embryos. Reduction of the maternal store completely alters the fates of different regions of the blastula so that animal cell fate is changed from epidermis and nervous system to epidermis only, equatorial cell fate is changed from mesoderm to ectoderm, and vegetal cell fate is changed from endoderm to mesoderm and ectoderm. Vegetal cells lose their capacity both to form endoderm and to release mesoderm-inducing signals. These results show that a single maternally expressed gene controls the patterning of the Xenopus blastula.
(C.J.W); frank.pigula@ulp.org (F.A.P.) Overline: Cardiovascular diseaseOne Sentence Summary: A soft robotic sleeve modeled on the structure of the human heart assists cardiovascular function in an ex vivo and in vivo porcine model of heart failure. Abstract:There is much interest in form-fitting, low modulus, implantable devices or soft robots that can mimic or assist in complex biological functions such as the contraction of heart muscle. Here we present a soft robotic sleeve that is implanted around the heart and actively compresses and twists to act as a cardiac ventricular assist device. The sleeve does not contact blood, obviating the need for anticoagulation therapy or blood thinners, and reduces complications with current ventricular assist devices such as clotting and infection. Our approach used a biologically inspired design to orient individual contracting elements or actuators in a layered helical and circumferential fashion, mimicking the orientation of the outer two muscle layers of the mammalian heart. The resulting implantable soft robot mimicked the form and function of the native heart, with a stiffness value of the same order of magnitude as native heart tissue. We demonstrated feasibility of this soft sleeve device for supporting heart function in a porcine model of acute heart failure. The soft robotic sleeve can be customized to patient-specific needs and may have the potential to act as a bridge to transplant for patients with heart failure.
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