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Xiaoping Ma, Andrea Reyna, Shailaja K. Mani, Martin M. Matzuk, and T. Rajendra Kumar. Biol Reprod 73:1182–1190. Published 10 August 2005; 10.1095/ biolreprod.105.043794
Interesting twist to sexual behavior Male sexual behavior arises from a complex interplay between hormones and neuronal circuits. Using a combination of knock-out technology and behavioral testing, Ma et al. (p. 1182) have identified a novel role for signaling through the activin type II receptor in this process. Despite normal levels of testosterone, coordination, ability to recognize and discriminate odors, and penile histology, mice lacking this receptor are deficient in a number of male-specific behaviors. Knock-out mice were found to have roughly half the activity levels of neural nitric oxide synthase (NOS), an enzyme that produces the gaseous transmitter NO. Interestingly, this reduction of activity was specific to the preoptic area of the hypothalamus and not associated with changes in NOS messenger RNA levels. This research thus not only reveals a novel role for activin signaling in sex behavior, it provides a basis for future studies of the cellular mechanisms underlying the regulation of sex behavior.
Tn5 Transposase-Mediated Mouse Transgenesis
Ryota Suganuma, Pawel Pelczar, Jean-Francois Spetz, Barbara Hohn, Ryuzo Yanagimachi, and Stefan Moisyadi. Biol Reprod 73:1157–1163. Published 3 August 2005; 10.1095/biolreprod.105.044669
Novel method for mouse transgenesis A variety of methods have been developed for producing transgenic animals, including ICSI, pronuclear injection, virus-mediated insertion, and ES cell-mediated approaches. On p. 1157, Suganuma et al. report a new method for producing transgenic mice by ICSI, using a Tn5 recognition sequence at both ends of a green fluorescent protein (GFP) transgene and introducing the transgene and hyperactive Tn5 transposase along with spermatozoa into unfertilized eggs. In the investigators' hands, this approach dramatically increased the efficiency of producing transgenic mice, with 11% of eggs injected and 22% of live births resulting in transmission of the transgene DNA and over 75% of transgenic mice expressing the GFP transgene. A drawback is that only a limited number of laboratories are able to do ICSI and will benefit, because the Tn5-mediated transgenesis does not improve the efficiency of the widely used pronuclear injection approach for producing transgenic mice. However, the potential impact of this new method is quite significant because of the increased efficiency gained from its use.
A Tale of Two Cells: Endocannabinoid-Signaling Regulates Functions of Neurons and Sperm
Herbert Schuel and Lani J. Burkman. Biol Reprod 73:1078–1086. Published 24 August 2005; 10.1095/biolreprod.105.043273
Insights from neurons into the sperm acrosome reaction On p. 1078, a minireview by Schuel and Burkman challenges readers to a new perspective on sperm by describing an interesting analogy between neurons and sperm. Both cell types contain cannabinoid receptors (CBR) for psychoactive drugs. These receptors can utilize as ligands both endogenous arachidonoylethanolamide (AEA) and delta-9-tetrahydrocannabinol (D9THC), the major psychoactive constituent of marijuana. In the presence of AEA, further neurotransmitter release is inhibited at excitatory synapses in neurons and analogously, AEA and D9THC can inhibit the acrosomal reaction (AR) in sperm. Thus AEA signaling may have a direct affect on sperm function in mammals by altering the AR and perhaps D9THC may produce similar effects in humans (leading to speculation on possible consequences for chronic marijuana smokers).
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