Controllable electrofusion of lipid vesicles: initiation and analysis of reactions within biomimetic containers

We present a microfluidic device that is able to trap multiple giant unilamellar vesicles (GUVs) and initiate electrofusion via integrated microelectrodes. PDMS posts were designed to trap and isolate two or more vesicles. Electrodes patterned onto the glass surface of the microchannels are able to apply a short, high voltage pulse across the traps for controllable electrofusion of the GUVs. The entire array of traps and electrodes are designed such that an average of 60 individual fusion experiments can be performed on-chip. An assay based on Förster resonance energy transfer (FRET) is performed to show successful lipid mixing. Not only can the device be used to record the dynamics of lipid membrane fusion, but it can be used for reaction monitoring by fusing GUVs containing reactants. We demonstrate this by fusing vesicles encapsulating femtolitre volumes of cobalt chloride or EDTA and monitoring the amount of the complexation product over time.

Microfluidic trapping of giant unilamellar vesicles to study transport through a membrane pore

We present a microfluidic platform able to trap single GUVs in parallel. GUVs are used as model membranes across many fields of biophysics including lipid rafts, membrane fusion, and nanotubes. While their creation is relatively facile, handling and addressing single vesicles remains challenging. The PDMS microchip used herein contains 60 chambers, each with posts able to passively capture single GUVs without compromising their integrity. The design allows for circular valves to be lowered from the channel ceiling to isolate the vesicles from rest of the channel network. GUVs containing calcein were trapped and by rapidly opening the valves, the membrane pore protein α-hemolysin (αHL) was introduced to the membrane. Confocal microscopy revealed the kinetics of the small molecule efflux for different protein concentrations. This microfluidic approach greatly improves the number of experiments possible and can be applied to a wide range of biophysical applications.

A high-resolution comparative map of porcine chromosome 4 (SSC4)

We used the IMNpRH2(12,000-rad) RH and IMpRH(7,000-rad) panels to integrate 2019 transcriptome (RNA-seq)-generated contigs with markers from the porcine genetic and radiation hybrid (RH) maps and bacterial artificial chromosome finger-printed contigs, into 1) parallel framework maps (LOD ≥ 10) on both panels for swine chromosome (SSC) 4, and 2) a high-resolution comparative map of SSC4, thus and human chromosomes (HSA) 1 and 8. A total of 573 loci were anchored and ordered on SSC4 closing gaps identified in the porcine sequence assembly Sscrofa9. Alignment of the SSC4 RH with the genetic map identified five microsatellites incorrectly mapped around the centromeric region in the genetic map. Further alignment of the RH and comparative maps with the genome sequence identified four additional regions of discrepancy that are also suggestive of errors in assembly, three of which were resolved through conserved synteny with blocks on HSA1 and HSA8.

Mapping and association of <i>GAD2</i> and <i>GIP</i> gene variants with feed intake and carcass traits in beef cattle (short communication)

Abstract. Glutamate decarboxylase 2 (GAD2) is a major autoantigen in insulin-dependent diabetes, while glucosedependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone. Both genes are involved in insulin secretion and play a role in the regulation of feed intake and metabolic rate in animals. In the present study, we assigned the bovine GAD2 and GIP by RH mapping to BTA 13 and BTA 19, respectively. We discovered SNPs from these genes by a PCR-sequencing approach. We identified one SNP (T/C transition) from the 14th intron of the bovine GAD2 gene and another SNP (A/C transversion) from the 4th intron of the bovine GIP gene. Genotyping over 300 animals from five different beef populations revealed that the average allelic frequency for the GAD2 allele A was 0.48 and allele B 0.52, while for the GIP allele A 0.80 and allele B 0.20, respectively. There were significant associations observed between the GAD2 and GIP gene variants and Average Daily Feed Intake (ADFI) (p<0.05) in beef cattle. In addition, the GAD2 SNP was also associated with Meat Percent (MP) (p<0.05), whereas the GIP SNP was also significantly associated with Backfat Thickness (BF) (p<0.05) and Ratio of Feed-to-Meat (RFM) (p<0.05). There were no significant effects found for other traits. Although both SNPs could be used as candidate markers for MAS to improve feed intake and carcass traits, further investigations in large populations and in other breeds are recommended in order to understand the effect of the GAD2 and GIP polymorphisms on these quantitative traits in beef cattle.

High-resolution comprehensive radiation hybrid maps of the porcine chromosomes 2p and 9p compared with the human chromosome 11

We are constructing high-resolution, chromosomal 'test' maps for the entire pig genome using a 12,000-rad WG-RH panel (IMNpRH2(12,000-rad))to provide a scaffold for the rapid assembly of the porcine genome sequence. Here we present an initial, comparative map of human chromosome (HSA) 11 with pig chromosomes (SSC) 2p and 9p. Two sets of RH mapping vectors were used to construct the RH framework (FW) maps for SSC2p and SSC9p. One set of 590 markers, including 131 microsatellites (MSs), 364 genes/ESTs, and 95 BAC end sequences (BESs) was typed on the IMNpRH2(12,000-rad) panel. A second set of 271 markers (28 MSs, 138 genes/ESTs, and 105 BESs) was typed on the IMpRH(7,000-rad) panel. The two data sets were merged into a single data-set of 655 markers of which 206 markers were typed on both panels. Two large linkage groups of 72 and 194 markers were assigned to SSC2p, and two linkage groups of 84 and 168 markers to SSC9p at a two-point LOD score of 10. A total of 126 and 114 FW markers were ordered with a likelihood ratio of 1000:1 to the SSC2p and SSC9p RH(12,000-rad) FW maps, respectively, with an accumulated map distance of 4046.5 cR(12,000 )and 1355.2 cR(7,000 )for SSC2p, and 4244.1 cR(12,000) and 1802.5 cR(7,000) for SSC9p. The kb/cR ratio in the IMNpRH2(12,000-rad) FW maps was 15.8 for SSC2p, and 15.4 for SSC9p, while the ratio in the IMpRH(7,000-rad) FW maps was 47.1 and 36.3, respectively, or an approximately 3.0-fold increase in map resolution in the IMNpRH(12,000-rad) panel over the IMpRH(7,000-rad) panel. The integrated IMNpRH(12,000-rad) andIMpRH(7,000-rad) maps as well as the genetic and BAC FPC maps provide an inclusive comparative map between SSC2p, SSC9p and HSA11 to close potential gaps between contigs prior to sequencing, and to identify regions where potential problems may arise in sequence assembly.

Mapping, expression, and association study of the bovine PSMC1 gene

The 26S ATP-dependent protease is composed of a 20S catalytic proteasome and two PA700 regulatory modules; it plays a central role in many regulatory pathways, such as cell cycle regulation, differentiation, and apoptosis. The PA700 complex is composed of multiple subunits, including at least six related ATPases and approximately 15 non-ATPase polypeptides. PSMC1 (proteasome 26S subunit, ATPase, 1) is one of these ATPases. In this study, we amplified a fragment of 507 bp from intron 9 of the bovine PSMC1 gene and found a SNP (G/A) at position 216 in the PCR fragment. Genotyping of 138 animals from four beef breeds revealed that the average frequency for allele A (G-base) was 0.4271 (0.3269-0.5517); for allele B (A-base) it was 0.5729 (0.4483-0.6731). This SNP is significantly associated with average daily feed intake (P < 0.01), average daily gain, finishing average daily gain, body length, ratio of feed to meat, backfat thickness, and loin-muscle area (P < 0.05). Our experimental data showed that animals with an AA genotype have a significantly lower food intake, grow faster, are longer in the body, and have less backfat and bigger loin muscle; hence, their ratio of feed to meat is significantly lower. We believe that the PSMC1 SNP is a potential candidate marker for marker-assisted selection in these traits. We also found that the bovine PSMC1 gene was expressed mainly in lung, testis, and spleen. In addition, we mapped the bovine PSMC1 gene on BTA10 by an RH mapping method.