Name: Collection and Washing of Sperm from the AcroSensE Mouse Model for Real-Time Imaging
Uploaded: 2023-10-13T14:20:00
Description: Watch this Scientific Journal Video about Collection and Washing of Sperm from the AcroSensE Mouse Model for Real-Time Imaging at JoVE.com

collection and washing of sperm from the acrosense mouse model for real-time imaging

Kombinera bildbehandling med ett system för tillförsel av stimulantia för att studera levande musspermier

Sperm acquire the ability to fertilize during a process called capacitation1. One endpoint of this process is that the sperm acquire the ability to undergo AE. Over two decades of data support the presence of a complex, multi-step model of AE in mammalian sperm (summarized in2,3). However, studying AE in live sperm is challenging, and currently available methods to monitor this process with adequate resolution are cumbersome and require multiple preparation steps4, are limited to the detection of the final step of AE (e.g., using PNA5), are limited to measurements of changes in cytosolic calcium (in contrast to acrosomal calcium dynamics), or are limited to measurements of either cytosolic calcium dynamics or AE6.
To overcome some of the key limitations of real-time AE studies under physiological conditions and to enable investigation of the interplay between calcium dynamics and AE, a unique mouse model was generated. In this mouse model, a fusion protein composed of the genetically encoded Ca2+-sensor (GCaMP3) and mCherry is expressed and targeted to the acrosome using an acrosin promoter and signaling peptide2. The targeted dual GCaMP3-mCherry sensor enables simultaneous real-time measurements of calcium concentrations and the status of the acrosomal contents in live sperm under physiological conditions using microscopy and a single-cell stimulant delivery system (Figure 1). As a component of the acrosomal matrix, membrane fusion, and AE would result in the loss of the photostable and pH-insensitive mCherry fluorescence from the sperm, as this protein diffuses out of the acrosome vesicle. In this regard, the model&#39;s ability to reflect the timing and occurrence of AE is akin to the benefits of the acrosome-targeted GFP mouse line7,8,9.
The GCaMP3 variant used in this transgenic mouse line has an approximate KD of 400 &#181;M and a dynamic range for Ca2+ of 10-4-10-3 M10, which is suitable for this vesicle. We showed that this combination of features of GCaMP3 could reveal fusion pore formation between the plasma membrane and the outer acrosomal membrane (OAM)2. The fusion pore detection is a result of the pore size being too small to allow the AcroSensE protein to disperse out of the acrosome (via loss of acrosome content) while providing a membrane &#34;channel&#34; that enables the influx of Ca2+ ions into the acrosome lumen, leading to an increase in fluorescence intensity of the GCaMP3.
The bright, monomeric, non-calcium-sensitive fluorescent protein mCherry supports visualization of the acrosome while the GCaMP3 signal is faint (e.g., prior to Ca2+ binding, Figure 2), and importantly, it also allows for the identification of acrosome-intact sperm cells suitable for imaging.
The following protocol describes the utilization of the unique AcroSensE mouse model and the methods for microscopy used experimentally to study AE and sperm calcium dynamics with high spatial and temporal resolution.

Författare i fokus: En teknik för avbildning av levande celler för att studera kalciumsignalering och akrosomexocytos i musspermier 

Realtidsavbildning av akrosomal kalciumdynamik och exocytos i levande musspermier

Our research goal is to better understand the molecular mechanisms that regulate sperm function, including the processes such as capacitation and fertilization. Specifically, we're exploring how membrane lipids activate calcium signaling and acrosome exocytosis. This protocol addresses the gap in our understanding of the interplay between capacitation, sperm activation, calcium signaling, and acrosome exocytosis.The advantages of this protocol include imaging sperm under physiological conditions, as well as its ability to simultaneously monitor both calcium signaling and acrosome exocytosis without the need for complicated preloading or standing procedures.

Watch this Scientific Journal Video about Collection and Washing of Sperm from the AcroSensE Mouse Model for Real-Time Imaging at JoVE.com

Collection and Washing of Sperm from the AcroSensE Mouse Model for Real-Time Imaging  

Insamling och tvättning av spermier från AcroSensE-musmodellen för realtidsavbildning

Börja med att samla in spermier från bitestikeln, isolerade från en transgen modellmus som uttrycker AcroSensE. Utför spermieinsamlingen i en 3,5 centimeter vävnadsodlingsskål som innehåller 0,5 milliliter MW-medium genom att tillåta en 15 minuters utsimningsprocedur vid 37 grader Celsius. Använd sedan en fin pincett och ta försiktigt bort eventuell bitestikelvävnad från uppsamlingsskålen.Överför mediet som innehåller spermierna till ett 15 ml koniskt rör och centrifugera suspensionen vid 100 G i en minut vid rumstemperatur med hjälp av en svängande skoprotor. Med hjälp av en plastpipett, samla MW-supernatanten som innehåller spermierna samtidigt som du kasserar eventuell pellet med grovt vävnadsskräp och överför den till ett runt bottenrör. Justera supernatantvolymen till en milliliter genom att tillsätta 500 mikroliter MW-medium förvärmt till 37 grader Celsius.Centrifugera blandningen vid 400 G i åtta minuter i rumstemperatur i ett rör med rund botten. Ta sedan försiktigt bort supernatanten samtidigt som du lämnar kvar den löst pelleterade sperman. Använd ett överföringsrör med stor borrning och suspendera spermierna igen genom att försiktigt knacka på röret manuellt, så kallad fingersnärtning.När spermierna är jämnt återsuspenderade, överför dem till ett nytt runt bottenrör.

Research

JoVE Journal

Developmental Biology

Collection and Washing of Sperm from the AcroSensE Mouse Model for Real-Time Imaging

Real-Time Imaging of Acrosomal Calcium Dynamics and Exocytosis in Live Mouse Sperm

Acrosome exocytosis (AE), in which the sperm&#39;s single exocytotic vesicle fuses with the plasma membrane, is a complex, calcium-dependent process ...