Binding of sperm protein Izumo1 and its egg receptor Juno drives Cd9 accumulation in the intercellular contact area prior to fusion during mammalian fertilization.

Little is known about the molecular mechanisms that induce gamete fusion during mammalian fertilization. After initial contact, adhesion between gametes only leads to fusion in the presence of three membrane proteins that are necessary, but insufficient, for fusion: Izumo1 on sperm, its receptor Juno on egg and Cd9 on egg. What happens during this adhesion phase is a crucial issue. Here, we demonstrate that the intercellular adhesion that Izumo1 creates with Juno is conserved in mouse and human eggs. We show that, along with Izumo1, egg Cd9 concomitantly accumulates in the adhesion area. Without egg Cd9, the recruitment kinetics of Izumo1 are accelerated. Our results suggest that this process is conserved across species, as the adhesion partners, Izumo1 and its receptor, are interchangeable between mouse and human. Our findings suggest that Cd9 is a partner of Juno, and these discoveries allow us to propose a new model of the molecular mechanisms leading to gamete fusion, in which the adhesion-induced membrane organization assembles all key players of the fusion machinery.

Safety of home parenteral nutrition in patients with amyotrophic lateral sclerosis: a French national survey.

We carried out a retrospective multicentre study to assess the safety of home parenteral nutrition (HPN) in patients with ALS. We reviewed the case records of patients from French ALS centres treated with HPN by central venous catheter (CVC) using an implantable port between January 2005 and October 2009. Seventy-three patients received HPN for a total of 11,908 catheter days. Twenty-seven patients experienced a total of 37 CVC related complications resulting in an incidence rate of 3.11 CVC complications/1000 catheter days, including 1.93 septic complications and 1.09 mechanical complications/1000 catheter days. Metabolic complications were frequent but without serious consequences on mortality. The use of the catheter for intravenous therapies in addition to HPN was identified as a septicaemia's risk factor (relative risk (RR) = 2.54, confidence interval (CI) 1.56-4.14, p = 0.04). In conclusion, HPN is an alternative procedure to PEG in advanced ALS patients. The incidence of complications appears to be comparable to data from the literature on HPN in other diseases. A prospective study comparing HPN and radiologic inserted gastrostomy (RIG) would allow comparison of the relative risk-benefit and survival of these procedures. The relation of CVC and RIG placement timing and the complications' occurrence should also be investigated.

Sperm SPACA6 protein is required for mammalian Sperm-Egg Adhesion/Fusion.

Three genes are known to be essential for gamete adhesion/fusion (Cd9, Izumo1 and Juno). Here, we confirmed that Spaca6 null males are infertile and showed that their sperm accumulate in the perivitelline space but are unable to fuse with oocyte. Like IZUMO1, SPACA6 which is expressed by human sperm, is remained on the equatorial segment after acrosomal reaction and is involved in human fertilization since an anti-SPACA6 antibody inhibited it. Despite the similarity of the phenotypes caused by Spaca6 and Izumo1 knockouts, these are not redundant and the essential relocation of IZUMO1 is not affected by the lack of SPACA6. We propose a model in which IZUMO1 and SPACA6 would be part of a molecular complex necessary for gamete fusion and that their concomitant presence would be required for the recruitment of another essential molecular actor, such as a fusogen, for the fusion to take place.