[Impact of VA-ECMO combined with IABP and timing on outcome of patients with acute myocardial infarction complicated with cardiogenic shock]

Objective: To investigate the impact of combined use and timing of arterial-venous extracorporeal membrane oxygenation (VA-ECMO) with intra-aortic balloon pump (IABP) on the prognosis of patients with acute myocardial infarction complicated with cardiogenic shock (AMICS). Methods: This was a prospective cohort study, patients with acute myocardial infarction and cardiogenic shock who received VA-ECMO support from the Heart Center of Lanzhou University First Hospital from March 2019 to March 2022 in the registration database of the Chinese Society for Extracorporeal Life Support were enrolled. According to combination with IABP and time point, patients were divided into VA-ECMO alone group, VA-ECMO+IABP concurrent group and VA-ECMO+IABP non-concurrent group. Data from 3 groups of patients were collected, including the demographic characteristics, risk factors, ECG and echocardiographic examination results, critical illness characteristics, coronary intervention results, VA-ECMO related parameters and complications were compared among the three groups. The primary clinical endpoint was all-cause death, and the safety indicators of mechanical circulatory support included a decrease in hemoglobin greater than 50 g/L, gastrointestinal bleeding, bacteremia, lower extremity ischemia, lower extremity thrombosis, acute kidney injury, pulmonary edema and stroke. Kaplan-Meier survival curves were used to analyze the survival outcomes of patients within 30 days of follow-up. Using VA-ECMO+IABP concurrent group as reference, multivariate Cox regression model was used to evaluate the effect of the combination of VA-ECMO+IABP at different time points on the prognosis of AMICS patients within 30 days. Results: The study included 68 AMICS patients who were supported by VA-ECMO, average age was (59.8±10.8) years, there were 12 female patients (17.6%), 19 cases were in VA-ECMO alone group, 34 cases in VA-ECMO+IABP concurrent group and 15 cases in VA-ECMO+IABP non-concurrent group. The success rate of ECMO weaning in the VA-ECMO+IABP concurrent group was significantly higher than that in the VA-ECMO alone group and the VA-ECMO+IABP non-concurrent group (all P<0.05). Compared with the ECMO+IABP non-concurrent group, the other two groups had shorter ECMO support time, lower rates of acute kidney injury complications (all P<0.05), and lower rates of pulmonary edema complications in the ECMO alone group (P<0.05). In-hospital survival rate was significantly higher in the VA-ECMO+IABP concurrent group (28 patients (82.4%)) than in the VA-ECMO alone group (9 patients) and VA-ECMO+IABP non-concurrent group (7 patients) (all P<0.05). The survival rate up to 30 days of follow-up was also significantly higher surviving patients within were in the ECMO+IABP concurrent group (26 cases) than in VA-ECMO alone group (9 patients) and VA-ECMO+IABP non-concurrent group (4 patients) (all P<0.05). Multivariate Cox regression analysis showed that compared with the concurrent use of VA-ECMO+IABP, the use of VA-ECMO alone and non-concurrent use of VA-ECMO+IABP were associated with increased 30-day mortality in AMICS patients (HR=2.801, P=0.036; HR=2.985, P=0.033, respectively). Conclusions: When VA-ECMO is indicated for AMICS patients, combined use with IABP at the same time can improve the ECMO weaning rate, in-hospital survival and survival at 30 days post discharge, and which does not increase additional complications.

Validation of Non-Invasive Preimplantation Genetic Screening Using a Routine IVF Laboratory Workflow

Embryo selection is needed to optimize the chances of pregnancy in assisted reproduction technology. This study aimed to validate non-invasive preimplantation genetic testing for aneuploidy (niPGT-A) using a routine IVF laboratory workflow. Can niPGT-A combined with time-lapse morphokinetics provide a better embryo-selection strategy? A total of 118 spent culture mediums (SCMs) from 32 couples were collected. A total of 40 SCMs and 40 corresponding trophectoderm (TE) biopsy samples (n = 29) or arrested embryos (n = 11) were assessed for concordance. All embryos were cultured to the blastocyst stage (day 5 or 6) in a single-embryo culture time-lapse incubator. The modified multiple annealing and looping-based amplification cycle (MALBAC) single-cell whole genome amplification method was used to amplify cell-free DNA (cfDNA) from the SCM, which was then sequenced on the Illumina MiSeq system. The majority of insemination methods were conventional IVF. Low cfDNA concentrations were noted in this study. The amplification niPGT-A and conventional PGT-A was 67.7%. Based on this study, performing niPGT-A without altering the daily laboratory procedures cannot provide a precise diagnosis. However, niPGT-A can be applied in clinical IVF, enabling the addition of blastocysts with a better prediction of euploidy for transfer.

P–659 Artificial intelligence (AI) as an assisting tool in generating patient-friendly corifollitropin alfa ovarian stimulation protocol during in vitro fertilization

Study question

How machine learning assisted in generating patient-friendly corifollitropin alfa protocol in normal responders?

Summary answer

In retrospective experiments, our machine learning model integrated physiological measurements of patients and clinical experience to generate a patient-friendly corifollitropin alfa protocol.

What is known already

Long-acting corifollitropin alfa can simplify the regimen, minimizing injections during the whole cycle. The previous study has described the patient-friendly protocol using corifollitropin alfa without routine pituitary suppression in normal responder can result in non-compromised clinical outcomes. Some studies showed machine learning can help with making clinical decisions and have the ability to learn from physiological measurements. Those methods effectuate certain points throughout short-acting menotropin protocols, however, there are still no robust AI tools for long-acting corifollitropin alfa protocols.

Study design, size, duration

1,309 cycles were collected at Stork Fertility Center from November 2016 to October 2019, and 1,221 cycles were available after data cleaning and applying exclusion criteria, which Anti-Mullerian Hormone (AMH) is lower than 2. The data from electronic medical records (EMRs) consisted of age, AMH, body weight, luteinizing hormone (LH), and estradiol (E2) concentrations measured on revisit. Evaluation is performed by one physician who has more than 20 years of experience in IVF. Participants/materials, setting, methods: The protocol generator consisted of 5 parts: doses of Elonva, trigger type, doses of recombinant follicle-stimulating hormone (rFSH), doses of recombinant luteinizing hormone (rLH), and day of oocyte retrieval. The protocol was predicted by age, AMH, and weight firstly, then fine-tuned by LH and E2 after the first revisit. We used the gradient boosting decision tree algorithm to learn the protocol. The dataset was randomly split into 80% for training and 20% for testing.

Main results and the role of chance

In classification, the model predicted the dose of Elonva achieved an accuracy of 0.913 and an AUC of 0.946, and trigger type got an accuracy of 0.901 and AUC of 0.852 only using features on stimulation day (SD) 1 and gained 0.012 and 0.056 in accuracy and AUC correspondingly after adding features on the first revisit day. In regression, the mean absolute error (MAE) of rFSH dose, rLH dose, and oocytes retrieved day was 156.30 IU, 232.75 IU, and 0.80 days respectively, and after refining, the MAE dropped to 92.37 IU, 100.07 IU, and 0.46 days. The error of predictions in rFSH and rLH was almost equal to half increments of rFSH (150 IU) and one increment rLH (75 IU). This indicated that our model could provide a better prediction of these clinical decisions with one revisit only.

Limitations, reasons for caution

The present study was a single-center retrospective, and only analyzed the data from normal responders, whose AMH was equal or greater than 2. Though, the recommendations of our system act as references, the physician will make the final decision.

Wider implications of the findings: Our result showed the potential of machine learning in generating protocols is promising. Recommendations generated by our model can provide the junior clinical teams to optimize the clinical plans and learn from the experience of experts. We look forward to applying our machine learning model to different protocols.

Trial registration number

Not applicable

O-086 End-to-end deep learning for recognition of ploidy status using time-lapse videos

Study question

Our Retrospective study is to investigate an end-to-end deep learning model in identifying ploidy status through raw time-lapse video.

Summary answer

Our deep learning model demonstrates a proof of concept and potential in recognizing the ploidy status.

What is known already

Since the time-lapse system has been introduced into the IVF lab, the relationship between morphogenetic and ploidy status has been often discussed. However, the result has not yet reached a united conclusion due to some limitations such as human labeling. Besides the statistical approach, deep learning models have been utilized for ploidy prediction. As such approaches are single image-based, the performance remains unpromising as previous statistical-based research. Therefore, in order to move further toward clinical application, better research design and approach are needed.

Study design, size, duration

A retrospective analysis of the time-lapse videos and chromosomal status from 690 biopsied blastocysts cultured in a time-lapse incubator (EmbryoScope+, Vitrolife) between January 2017 and August 2018 in the Lee Women’s Hospital were assessed. The ploidy status of the blastocyst was derived from the PGT-A using high-resolution next-generation sequencing (hr-NGS). Embryo videos were obtained after normal fertilization through the intracytoplasmic sperm injection or conventional insemination.

Participants/materials, setting, methods

By randomly dividing the data into 80% and 20%, we developed our deep learning model based on Two-Stream Inflated 3D ConvNets(I3D) network. This model was trained by the 80% time-lapse videos and the PGT-A result. The remaining 20% has been tested by feeding the time-lapse video as input and the PGT-A prediction as output. Ploidy status was classified as Group 1 (aneuploidy) and Group 2 (euploidy and mosaicism).

Main results and the role of chance

Time-lapse videos were divided into 3-time partitions: day 1, day 1 to 3, and day 1 to 5. Deep learning models have been fed by RGB and optical flow. Combining 3 different time partitions with RGB, optical flow, and fused result from RGB and optical flow, we received nine sets of test results. According to the results, the longest time partition with the fusion method has the highest AUC result as 0.74, which appeared higher than the other eight experimental settings with a maximum increase of 0.17.

Limitations, reasons for caution

The present study is retrospective and future prospective research would help us to identify more key factors and improve this model. In addition, expanding sample size combined with cross-centered validation will also be considered in our future approach.

Wider implications of the findings

Group 1 and Group 2 approach provided deselection of aneuploidy embryos, while future deep learning approaches toward high mosaicism, low mosaicism, and euploidy will be needed, in order to provide a better clinical application.

Trial registration number

CS18082

Use of Non-Destructive Measurements to Identify Cucurbit Species (Cucurbita maxima and Cucurbita moschata) Tolerant to Waterlogged Conditions

Limited information is available regarding the physiology of squash plants grown under waterlogging stress. The objectives of this study were to investigate the growth and physiological performances of three cucurbit species, Cucurbita maxima cultivar (cv.) OK-101 (OK) and Cucurbita moschata cv. Early Price (EP) and Strong Man (SM), in response to waterlogging conditions, and to develop a precise, integrated, and quantitative non-destructive measurement of squash genotypes under stress. All tested plants were grown in a growth chamber under optimal irrigation and growth conditions for a month, and the pot plants were then subjected to non-waterlogging (control) and waterlogging treatments for periods of 1, 3, 7, and 13 days (d), followed by a 3-d post-waterlogging recovery period after water drainage. Plants with phenotypes, such as fresh weight (FW), dry weight (DW), and dry matter (DM) of shoots and roots, and various physiological systems, including relative water content (RWC), soil and plant analysis development (SPAD) chlorophyll meter, ratio of variable/maximal fluorescence (Fv/Fm), quantum photosynthetic yield (YII), normalized difference vegetation index (NDVI), and photochemical reflectance index (PRI) values, responded differently to waterlogging stress in accordance with the duration of the stress period and subsequent recovery period. When plants were treated with stress for 13 d, all plants exhibited harmful effects to their leaves compared with the control, but EP squash grew better than SM and OK squashes and exhibited stronger tolerance to waterlogging and showed less injury. Changes in the fresh weight, dry weight, and dry matter of shoots and roots indicated that OK plants suffered more severely than EP plants at the 3-d drainage period. The values of RWC, SPAD, Fv/Fm, YII, NDVI, and PRI in both SM and OK plants remarkably decreased at waterlogging at the 13-d time point compared with controls under identical time periods. However, the increased levels of SPAD, Fv/Fm, YII, NDVI, and PRI observed on 7 d or 13 d of waterlogging afforded the EP plant leaf with improved waterlogged tolerance. Significant and positive correlations were observed among NDVI and PRI with SPAD, Fv/Fm, and YII, indicating that these photosynthetic indices can be useful for developing non-destructive estimations of chlorophyll content in squashes when screening for waterlogging-tolerant plants, for establishing development practices for their cultivation in fields, and for enhanced cultivation during waterlogging in frequently flooded areas.

1176Hepatocyte growth factor has prognostic utility in light chain and transthyretin cardiac amyloidosis

Background

With the advent of multiple novel therapeutics for light chain (AL) and transthyretin (ATTR) amyloidosis, there is a critical need for validated prognostic markers in cardiac amyloidosis. A discriminatory serum biomarker may improve prognostic and staging systems in AL and ATTR cardiac amyloidosis.

Purpose

Our objective was to test the hypothesis that hepatocyte growth factor (HGF) is associated with clinical outcomes in patients with AL and ATTR cardiac amyloidosis.

Methods

102 patients with AL or ATTR and suspected cardiac involvement were prospectively enrolled. HGF, NT-proBNP, troponin-T, and eGFR were measured upon study enrollment. Cardiac involvement was established by 1) endomyocardial biopsy, or 2) non-cardiac biopsy with concentric hypertrophy on echocardiography, low voltage or pseudo-infarction on ECG, elevated NT-proBNP or troponin-T, or characteristic delayed myocardial enhancement on cardiac MRI. Patients were followed for the occurrence of all-cause mortality, cardiac transplantation, and left-ventricular assist device implantation.

Results

Of the total amyloidosis cohort, 72 had cardiac involvement while 30 had non-cardiac disease. HGF, NT-proBNP, and troponin-T levels were significantly higher in patients with cardiac involvement than in patients with non-cardiac disease (p<0.05 for all comparisons). Over a median follow-up period of 1.9 years there were 20 deaths, 1 cardiac transplant, and 1 left-ventricular assist device implant, all in patients with cardiac involvement. Patient stratification by cut-off levels of NT-proBNP (332 pg/mL), troponin-T (35 ng/L), and eGFR (45 mL/min/1.73m2) used in published staging models for AL and ATTR cardiac amyloidosis showed no association between abnormal biomarker level and adverse clinical outcome (p>0.05). In contrast, stratification by HGF level of 310 pg/mL (identified by the Youden Index for cardiac involvement by AL and ATTR in our cohort) showed that elevated HGF was associated with worse clinical outcomes (p=0.0211). Furthermore, event-free survival was worse in patients with elevated HGF, with survival curves diverging soon after enrollment (p=0.0730).

HGF is Prognostic in Cardiac Amyloidosis

Conclusions

Elevated HGF is associated with worse clinical outcomes in patients with AL and ATTR cardiac amyloidosis and has potential for clinical utility.

Synthesis of one-dimensional TiO2/V2O5 branched heterostructures and their visible light photocatalytic activity towards Rhodamine B

We present the synthesis and visible-light-induced catalytic activity of one-dimensional (1D) TiO(2)/V(2)O(5) branched heterostructures. The 1D TiO(2)/V(2)O(5) heterostructures were prepared by RF reactive magnetron sputtering of V(2)O(5) onto electrospun TiO(2) nanofibers. Then, the samples were annealed at 300 °C for 2 h in air ambient to form the 1D TiO(2)/V(2)O(5) branched heterostructures. The photodecomposition rate of Rhodamine B (RhB) by the 1D TiO(2)/V(2)O(5) branched heterostructures under visible light was much faster than that of pure TiO(2) nanofibers, revealing that the visible-light-induced catalytic activity of the 1D TiO(2)/V(2)O(5) branched heterostructures was greatly improved. The enhancement of the photocatalytic activity of the 1D TiO(2)/V(2)O(5) branched heterostructures can be ascribed to the coupling with a small bandgap semiconductor material V(2)O(5), where the absorption range is extended, the photogenerated electrons and holes are highly separated and the surface charge carrier transfer rate is promoted.

Particulate matter characteristics during agricultural waste burning in Taichung City, Taiwan

Agricultural waste burning is performed after harvest periods in June and November in Taiwan. Typically, farmers use open burning to dispose of excess rice straw. PM(2.5) and PM(2.5-10) measurements were conducted at National Chung Hsing University in Taichung City using a dichotomous sampler. The sampling times were during straw burning periods after rice harvest during 2002-2005. Ionic species including SO(4)(2-), NO(3)(-), NH(4)(+), K(+), Ca(2+), Cl(-) and Na(+) and carbonaceous species (EC and OC) in PM(2.5) and PM(2.5-10) were analyzed. The results showed that the average PM(2.5) and PM(2.5-10) concentrations were 123.6 and 31.5 microg m(-3) during agricultural waste burning periods and 32.6 and 21.4 microg m(-3) during non-waste burning periods, respectively. The fine aerosol ionic species including Cl(-), K(+) and NO(3)(-) increased 11.0, 6.7 and 5.5 times during agricultural burning periods compared with periods when agricultural waste burning is not performed. K(+) was found mainly in the fine mode during agricultural burning. High nitrogen oxidation ratio was found during agricultural waste burning periods which might be caused by the conversion of Nitrogen dioxide (NO(2)) to NO(3)(-). It is concluded that agricultural waste burning with low dispersion often causes high PM(2.5) and gases pollutant events.

Isoform-specific effects of apolipoprotein E on atherogenesis: gene transduction studies in mice

BACKGROUND

We recently used a bone marrow-based gene therapy approach to show that small amounts of retrovirus-derived human apolipoprotein E3 (apoE3) produced by macrophages are protective against early atherosclerosis in apoE-deficient mice.

METHODS AND RESULTS

In the present study, we evaluated whether the effect produced by macrophage-derived apoE3 is related to its ability to bind cellular membranes. To this end, we used apoE2 and apoEcys142, dysfunctional human variants with reduced binding to the LDL receptor or to heparan sulfate proteoglycans, respectively. ApoE-deficient mice, 5 weeks of age, received transplants of apoE(-/-) bone marrow cells transduced with either parental retrovirus or apoE3, apoE2, or apoEcys142 retroviral vectors. Human apoE was detected by ELISA in the serum of apoE3, apoE2, and apoEcys142 mice as early as 4 weeks after bone marrow transplantation, and at 8 weeks, plasma apoE levels were 55.5+/-20.3, 50.5+/-8.7, and 15.3+/-7.3 microgram/dL, respectively. In all groups, cholesterol levels increased with age but were not affected by apoE expression. As previously demonstrated, the lesion area in male apoE3 mice (3808+/-2224 micrometer(2)/section) was 40% smaller than that in control mice (6503+/-3475 micrometer(2)/section). In apoE2 mice, however, the lesion area was similar to that of controls (5991+/-2771 micrometer(2)/section), and apoEcys142 mice showed an unexpected and significant increase in lesion size (10 320+/-6128 micrometer(2)/section). Thus, transplantation with marrow transfected with receptor binding-defective apoE variants did not replicate the antiatherogenic effect of apoE3.

CONCLUSIONS

These data provide in vivo evidence suggesting that macrophage-derived apoE delays development of atherosclerosis through a receptor-dependent pathway.

Increased cholesterol efflux in apolipoprotein AI (ApoAI)-producing macrophages as a mechanism for reduced atherosclerosis in ApoAI((-/-)) mice

The concentration of apolipoprotein (apo) AI in the artery wall is thought to enhance cellular cholesterol efflux and protect against atherosclerosis. It has been shown that although macrophages do not make apoAI, they respond to it by increased cholesterol efflux. We hypothesized that macrophage production of apoAI would increase cholesterol efflux and reduce atherogenesis. In this study, we produced mice expressing human apoAI under the control of the macrophage-specific scavenger receptor-A promoter (mphi-AI). Human apoAI was detectable in the serum HDL fraction of mphi-AI transgenic mice at concentrations too low to affect serum cholesterol or HDL levels. Immunoblotting showed the presence of human apoAI in transgenic macrophage culture supernatants, mostly as lipoprotein-free protein, with a small component associated with HDL-like particles. Atherosclerosis studies using apoAI((-/-)) mice transplanted with mphi-AI bone marrow showed that in the absence of macrophage-derived apoE, local expression of apoAI reduced diet-induced lesions in the proximal aorta. Additionally, mphi-AI macrophages showed a 40% increase in cholesterol efflux compared with control macrophages. These data support the hypothesis that apoAI production by macrophages in the artery wall is protective against atherosclerosis. This protection is likely mediated by increased cholesterol efflux and decreased foam cell formation in vivo.

Epithelial sodium channels and hypertension

Hypertension is a major risk factor for heart attacks, stroke, and kidney failure. It is estimated to cause as many as 25% of all deaths in the United States, particularly for African Americans, in whom the disease is both more common and more severe. Essential hypertension is a multifactorial disorder influenced by both genetic and environmental factors. Physiological studies have shown that the kidneys play an important role in the maintenance of sodium balance, extracellular fluid volume, and long-term control of blood pressure. The sodium transporters in the kidney affect the amount of sodium and water reabsorption in the nephron and thus control extracellular fluid volume and blood pressure. Of the renal sodium transporters, the amiloride-sensitive epithelial sodium channels (ENaC), which are responsible for the rate-limiting step of sodium reabsorption in the distal nephron, are therefore important candidates in the development of hypertension. Moreover, mutations in this channel have been shown to cause a rare form of heritable hypertension (Liddle's syndrome), and genetic linkage studies show that the beta- and gamma-subunits are linked to systolic blood pressure. Several polymorphisms have been identified in the beta- and gamma-subunits of this channel, of which the beta-T594M variant is of particular interest. This variant is found in individuals of African American descent and not in Caucasians and may be associated with hypertension in some populations of African descent. Lymphocytes from individuals with this variant channel show an increased sodium conductance in response to cAMP in vitro. Studying the polymorphic variants in the various subunits of ENaC may further our understanding of the mechanisms that underlie sodium balance in mammals. These variants will provide an avenue to identify molecular targets for new diagnostic and therapeutic tools in the clinical treatment of hypertension.

Genetic markers at the leptin (OB) locus are not significantly linked to hypertension in African Americans

Increased body mass index (BMI) has been correlated with increased blood pressure in human populations. To examine the role of the leptin gene (OB) in essential hypertension in African Americans, we performed affected sib pair analysis on a set of 103 hypertensive African American sibships using four highly polymorphic markers at the human leptin locus. No evidence of linkage was detected between these markers and the phenotype of essential hypertension either in these sibships or in a severely obese subset of 46 sibships in which each sibling had a BMI > or = 85th percentile for the US population. Using BMI rather than hypertension as a quantitative trait, we found significant linkage for the marker D7S504 (P=0.029) but not for the other markers. Significance strengthened in the overweight subset of sibships for this marker (P=0.001), and there was a trend of lower P values for the other three markers. However, multipoint analysis with the use of all four markers simultaneously to estimate linkage between BMI and the leptin locus did not demonstrate a statistically significant relationship. Analysis of the coding region of the leptin gene (exons 2 and 3) by single-strand conformational polymorphism revealed a rare Ile-Val polymorphism at amino acid 45 but revealed no other alterations. These results suggest that the OB gene is not a major contributor to the phenotype of essential hypertension in African Americans, although a minor contribution to the phenotype of extreme obesity in this group cannot be ruled out.

Loss of protein kinase C inhibition in the beta-T594M variant of the amiloride-sensitive Na+ channel

We previously reported the presence of a novel variant (beta-T594M) of the amiloride-sensitive Na+ channel (ASSC) in which the threonine residue at position 594 in the beta-subunit has been replaced by a methionine residue. Electrophysiological studies of the ASSC on Epstein-Barr virus (EBV)-transformed lymphocytes carrying this variant showed that the 8-(4-chlorophenylthio) adenosine 3':5'-cyclic monophosphate (8cpt-cAMP)-induced responses were enhanced when compared to wild-type EBV-transformed lymphocytes. Furthermore, in wild-type EBV-transformed cells, the 8cpt-cAMP-induced response was totally blocked by the phorbol ester, phorbol 12-myristate 13-acetate (PMA). This inhibitory effect of PMA was blocked by a protein kinase C inhibitor, chelerythrine. We now have identified individuals who are homozygous for this variant, and showed that PMA had no effect on the 8cpt-cAMP-induced responses in the EBV-transformed lymphocytes from such individuals. Cells heterozygous for this variant showed mixed responses to PMA, with the majority of cells partially inhibited by PMA. Our results demonstrate that an alteration in a single amino acid residue in the beta-subunit of the ASSC can lead to a total loss of inhibition to PMA, and establish the beta-subunit as having an important role in conferring a regulatory effect on the ASSC of lymphocytes.

A novel variant of the beta-subunit of the amiloride-sensitive sodium channel in African Americans

The amiloride-sensitive sodium channel is responsible for the rate-limiting step of sodium reabsorption in the distal renal tubule, and thus may play a key role in the maintenance of sodium balance and blood pressure. In this study, a genetic variant that results in a change of threonine to methionine at amino acid 594 (T594 M) in the carboxy-terminus of the beta-subunit of the amiloride-sensitive sodium channel has been identified. This variant was present in 6.1% of African-American subjects (N = 231) but was not seen in Caucasians (N = 192). Whole cell voltage clamp of B-lymphocytes from individuals with the T594 M variant showed similar basal membrane slope conductance, compared with the wild-type but increased response to cAMP analog.

Molecular cloning and physical and genetic mapping of a novel human Na+/H+ exchanger (NHE5/SLC9A5) to chromosome 16q22.1

A human genomic clone for a novel fifth member of the Na+/H+ exchanger (NHE) family, NHE5 (gene symbol SLC9A5), has been isolated and partially sequenced. The deduced amino acid sequence of two exons, containing 154 codons, exhibits 59-73% identity to the other members of the NHE family, with closest similarity to NHE3. Northern blot analysis demonstrated that the NHE5 gene is expressed in brain, testis, spleen, and skeletal muscle. Fluorescence in situ hybridization analysis of a cosmid containing NHE5 to human metaphase chromosomes localized the NHE5 gene to the cytogenetic interval 16q21-q22. A panel of somatic cell hybrids containing various portions of chromosome 16 was used to refine further the placement of NHE5 within band 16q22.1. A polymorphic dinucleotide (GT/CA)n repeat contained in the NHE5 cosmid was identified and developed into a microsatellite PCR marker. This was typed in a subset of the CEPH (Centre d'Etude du Polymorphisme Humain) families to place it on a genetic map of the human genome. Pairwise linkage analysis of this marker showed that it was linked to marker D16S421 with a maximal lod score of 35.21 at a recombination fraction (theta) of 0.000, in complete concordance with its chromosomal localization by physical mapping. Multipoint linkage analysis placed NHE5 between the flanking markers D16S421 and D16S512. The cloning of this new member of the sodium hydrogen exchanger family, its chromosomal localization, and the discovery of a polymorphic marker for it now make it feasible to study the possible involvement of this gene in disorders of Na+/H+ transport.

Molecular cloning and physical and genetic mapping of the human anion exchanger isoform 3 (SLC2C) gene to chromosome 2q36

A human clone corresponding to the gene encoding anion exchanger isoform 3 (AE3) (approved gene symbol SLC2C) has been isolated and partially sequenced. Oligonucleotide primers based on this sequence were used in a polymerase chain reaction to specifically amplify a segment of the human gene from a panel of human-rodent somatic cell hybrids, allowing the assignment of AE3 to chromosome 2. To map AE3 more precisely to a cytogenetic band on chromosome 2, the AE3 cosmid was used as a probe in fluorescence in situ hybridization to human metaphase chromosomes. Fractional length measurements were made, and AE3 mapped at high resolution to the cytogenetic band 2q36. A polymorphic dinucleotide (GT/CA)n repeat marker was developed from sequences in the AE3 cosmid and typed on a subset of the CEPH families. Multipoint linkage analysis placed the AE3 gene between D2S128 and D2S126 on a genetic map of chromosome 2, corroborating the chromosomal localization of AE3 obtained by physical mapping methods.

Identification of disease genes by positional cloning

Positional cloning or reverse genetics is a combination of techniques that has been extraordinarily successful in finding the genes that cause many inherited disorders, including some that affect the cardiovascular system. This approach consists of finding a DNA marker that cosegregates with the disorder and then using the tools of molecular biology to examine systematically the DNA in the vicinity of such a marker until the gene is identified. In addition to the availability of preclinical diagnostic tests for individuals at risk, the identification of such genes might also provide the basis for targeted drug design. In the longer term, with the emerging technologies for the delivery of genes into cells, finding the genes that cause inherited disorders raises the possibility of eventual therapeutic intervention.