Isogenic pairs of induced-pluripotent stem-derived endothelial cells identify DYRK1A/PPARG/EGR1 pathway is responsible for Down syndrome-associated pulmonary hypertension.

Down syndrome (DS) is the most prevalent chromosomal disorder associated with a higher incidence of pulmonary arterial hypertension (PAH). The dysfunction of vascular endothelial cells (ECs) is known to cause pulmonary arterial remodeling in PAH, although the physiological characteristics of ECs harboring trisomy 21 (T21) are still unknown. In this study, we analyzed the human vascular ECs by utilizing the isogenic pairs of T21-induced pluripotent stem cells (iPSCs) and corrected disomy 21 (cDi21)-iPSCs. In T21-iPSC-derived ECs, apoptosis and mitochondrial reactive oxygen species (mROS) were significantly increased, and angiogenesis and oxygen consumption rate (OCR) were significantly impaired as compared with cDi21-iPSC-derived ECs. The RNA-sequencing identified that EGR1 on chromosome 5 was significantly upregulated in T21-ECs. Both EGR1 suppression by siRNA and pharmacological inhibitor could recover the apoptosis, mROS, angiogenesis, and OCR in T21-ECs. Alternately, the study also revealed that DYRK1A was responsible to increase EGR1 expression via PPARG suppression, and that chemical inhibition of DYRK1A could restore the apoptosis, mROS, angiogenesis, and OCR in T21-ECs. Finally, we demonstrated that EGR1 was significantly upregulated in the pulmonary arterial ECs from lung specimens of a patient with DS and PAH. In conclusion, DYRK1A/PPARG/EGR1 pathway could play a central role for the pulmonary EC functions and thus be associated with the pathogenesis of PAH in DS.

Gene correction and overexpression of TNNI3 improve impaired relaxation in engineered heart tissue model of pediatric restrictive cardiomyopathy.

Research on cardiomyopathy models using engineered heart tissue (EHT) created from disease-specific induced pluripotent stem cells (iPSCs) is advancing rapidly. However, the study of restrictive cardiomyopathy (RCM), a rare and intractable cardiomyopathy, remains at the experimental stage because there is currently no established method to replicate the hallmark phenotype of RCM, particularly diastolic dysfunction, in vitro. In this study, we generated iPSCs from a patient with early childhood-onset RCM harboring the TNNI3 R170W mutation (R170W-iPSCs). The properties of R170W-iPSC-derived cardiomyocytes (CMs) and EHTs were evaluated and compared with an isogenic iPSC line in which the mutation was corrected. Our results indicated altered calcium kinetics in R170W-iPSC-CMs, including prolonged tau, and an increased ratio of relaxation force to contractile force in R170W-EHTs. These properties were reversed in the isogenic line, suggesting that our model recapitulates impaired relaxation of RCM, i.e., diastolic dysfunction in clinical practice. Furthermore, overexpression of wild-type TNNI3 in R170W-iPSC-CMs and -EHTs effectively rescued impaired relaxation. These results highlight the potential efficacy of EHT, a modality that can accurately recapitulate diastolic dysfunction in vitro, to elucidate the pathophysiology of RCM, as well as the possible benefits of gene therapies for patients with RCM.

A case of truncus arteriosus with severe heart failure and pulmonary stenosis: bridge to transplant candidacy with surgical correction and a ventricular-assist device.

Ventricular-assist device therapy for small patients with congenital heart disease is challenging due to its complex anatomy and hemodynamics. We describe a 3-year-old patient with heart failure with truncus arteriosus in the palliative stage. The patient underwent palliative right ventricular outflow tract reconstruction following bilateral pulmonary artery banding. At 6 months of age, the patient developed severe truncal valve regurgitation and left ventricular dysfunction. Emergent truncal valve replacement with a mechanical valve was performed, but left ventricular dysfunction persisted. At 3 years of age, the patient developed acute progression of heart failure triggered by influenza infection. The patient was intubated and transferred to our center to determine the indication for heart transplantation. On the second day after admission, signs of multiorgan failure appeared. Emergent ventricular-assist device implantation for both ventricles was performed with truncal valve closure, ventricular septal defect closure, atrial septal defect closure, and re-right ventricular outflow tract reconstruction. The right ventricular-assist device was successfully removed on the seventh postoperative day. Due to the small pulmonary arteries, severe pulmonary stenosis persisted after ventricular-assist device implantation, but it gradually improved with multiple pulmonary angioplasties. The patient was registered in the Japanese organ transplant network and is awaiting a donor organ in a stable condition.

Trans-subclavian approach for Impella CP implantation using the chimney graft in a pediatric patient with fulminant myocarditis during extracorporeal support.

Impella is a device effective for the treatment of cardiogenic shock. However, among small children, its application has limitations due to left ventricle size and vasculature and the turning diameter of the aortic arch. Herein, we report an 11-year-old girl with fulminant myocarditis who was successfully managed with Impella CP implantation via the right subclavian artery using a polyethylene terephthalate chimney graft. Compared with insertion via the femoral artery, this method has several advantages. That is, it can address limitations in aortic arch diameter and facilitate equable fixation of the Impella device in small pediatric patients.

Outcomes of Restrictive Cardiomyopathy in Japanese Children　- A Retrospective Cohort Study.

BACKGROUND: There has been no nationwide survey on the prognosis of pediatric restrictive cardiomyopathy (RCM) in Japan; therefore, this retrospective multicentered study was designed to investigate the long-term survival rate of pediatric patients with RCM in Japan.Methods and Results: A multicentered, retrospective observational study was performed between 1990 and 2014 and included patients diagnosed with RCM who were aged <18 years from 18 Japanese institutions. A total of 54 patients were diagnosed with RCM. The median age at diagnosis was 4.4 years, and the median duration of observation was 2.2 years at the time of this study. Of these patients, 54% had symptoms, including heart failure. Twelve patients died without heart transplantation, mostly due to heart failure. The median time to death from diagnosis was 2.5 years. Freedom from death at 1, 5, and 10 years was 91%, 68%, and 62%, respectively. Death occurred within 5 years of diagnosis in most patients. Twenty-two patients underwent heart transplantation. Freedom from heart transplantation at 1, 5, and 10 years was 77%, 58%, and 53%, respectively. Freedom from death or heart transplantation at 1, 5, and 10 years was 72%, 40%, and 34%, respectively. The presence of symptoms was a risk factor for death or transplantation. CONCLUSIONS: The prognosis of pediatric RCM is poor, and the heart transplantation rate is low in Japan.

Immunogenicity of SARS-CoV-2 vaccination in adolescents with cardiac disease.

BACKGROUND: Although widely reported to affect older adults more, coronavirus disease 2019 (COVID-19) also affects adolescents, especially those with co-morbidities, including heart diseases. The safety and efficacy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccines has been established in healthy adolescents, yet there are few data for humoral and cellular immunogenicity in adolescents with cardiac diseases. METHODS: We evaluated anti-spike antibodies, neutralizing activities, and interferon-gamma production prior to and after SARS-CoV-2 vaccination in adolescents with cardiac diseases and healthy controls. RESULTS: Five healthy adolescents and 26 patients with cardiac diseases, including congenital heart disease (CHD, n = 10), dilated cardiomyopathy (DCM, n = 4), idiopathic pulmonary arterial hypertension (IPAH, n = 4), and those post-heart transplantation (post-HTx, n = 8) were enrolled. No severe adverse events, including myocarditis and pericarditis, were noted, even in patients with severe heart failure. Febrile events were noted after 21 of 62 injections (34%). All the healthy adolescents and 21 of the 26 patients (81%) showed sufficient elevation of neutralizing antibodies after the second dose of vaccination. Neutralizing antibodies and cellular immunity were absent in four of the eight post-HTx patients and one with single ventricle CHD. There was no correlation between the anti-spike and neutralizing antibody titers and interferon-gamma levels. When comparing the clinical characteristics of the patients post-HTx who did or did not acquire antibodies, there was no significant difference in the immunosuppressant types and trough levels. CONCLUSIONS: SARS-CoV-2 mRNA vaccine has efficient immunogenicity for adolescents with CHD, IPAH, and DCM. Half of post-HTx patients could not acquire sufficient humoral immunity.

Cardiac Fibroblasts Play Pathogenic Roles in Idiopathic Restrictive Cardiomyopathy.

BACKGROUND: Restrictive cardiomyopathy (RCM) is characterized by impaired ventricular relaxation. Although several mutations were reported in some patients, no mutations were identified in cardiomyocyte expressing genes of other patients, indicating that pathological mechanisms underlying RCM could not be determined by cardiomyocytes only. Cardiac fibroblasts (CFs) are a major cell population in the heart; however, the pathological roles of CFs in cardiomyopathy are not fully understood.Methods and Results:This study established 4 primary culture lines of CFs from RCM patients and analyzed their cellular physiology, the effects on the contraction and relaxation ability of healthy cardiomyocytes under co-culture with CFs, and RNA sequencing. Three of four patients hadTNNI3mutations. There were no significant alterations in cell proliferation, apoptosis, migration, activation, and attachment. However, when CFs from RCM patients were co-cultured with healthy cardiomyocytes, the relaxation velocity of cardiomyocytes was significantly impaired both under direct and indirect co-culture conditions. RNA sequencing revealed that gene expression profiles of CFs in RCM were clearly distinct from healthy CFs. The differential expression gene analysis identified that several extracellular matrix components and cytokine expressions were dysregulated in CFs from RCM patients. CONCLUSIONS: The comprehensive gene expression patterns were altered in RCM-derived CFs, which deteriorated the relaxation ability of cardiomyocytes. The specific changes in extracellular matrix composition and cytokine secretion from CFs might affect pathological behavior of cardiomyocytes in RCM.

Riociguat can ameliorate bronchopulmonary dysplasia in the SU5416 induced rat experimental model.

BACKGROUND: Bronchopulmonary dysplasia (BPD) is a chronic lung disease in premature neonates. Classical BPD is caused by hyperoxia and high-pressure mechanical ventilation, whereas BPD in recent era is caused by impaired pulmonary angiogenesis and alveolarization in extreme prematurity. Although sildenafil was reported to be effective in a hyperoxia-induced rat BPD model, several clinical trials could not demonstrate any significant improvement in the respiratory statuses of BPD infants. Riociguat is a soluble guanylate cyclase stimulator that increases cyclic guanosine monophosphate activity in a nitric oxide independent manner. However, a beneficial effect in BPD has not been established yet. METHODS AND RESULTS: We established BPD model in rats by injection of SU5416 on day 1 followed by maintenance under normoxia, which resulted in oversimplified alveoli, sparse pulmonary capillary vessels, severe pulmonary hypertension, and growth retardation, which mimicked the features observed in recent clinical management of BPD. We administered riociguat from day 10, when BPD rats exhibited growth retardation. Histological analyses demonstrated that riociguat treatment significantly but partially ameliorated lung alveolarization, vascularization, and pulmonary hypertension. However, the survival rate was not significantly improved by riociguat treatment. CONCLUSIONS: Riociguat could ameliorate pulmonary alveolarization, vascularization, and hypertension in the SU5416 induced BPD rat model, but could not improve the overall survival.

Pediatric patient with restrictive cardiomyopathy on staged biventricular assist device support with Berlin Heart EXCOR® underwent heart transplantation successfully: the first case in Japan.

Pure restrictive cardiomyopathy is a strong risk factor for poor outcomes in children with cardiomyopathy on ventricular assist devices. Owing to concomitant right heart failure, children with end-staged restrictive cardiomyopathy who are supported with a ventricular assist device often require a biventricular assist device, which is another risk factor for waitlist mortality in heart transplantation candidates. Herein, we report the case of a 3-year-old boy with pure restrictive cardiomyopathy who successfully underwent heart transplantation after 12 months of support with staged biventricular assist devices. Owing to the progression of diastolic dysfunction, the left ventricular assist device could not provide adequate circulation support. Despite the provision of biventricular assist device support, the patient required a complex management strategy that involved balancing the left and right ventricular assist device supports. We were able to stabilize the patient by careful synchronization of the supports and proceeded to heart transplantation. TRIAL REGISTRATION: Clinical Registration No.: Institutional Review Board of Osaka University Hospital, approval no. 16105.

Evaluation of the Newly Developed Adenosine Diphosphate-Induced Platelet Aggregation Level System in Aggregometer on Automated Coagulation Analyzer.

BACKGROUND: Light transmission aggregometry (LTA) is the gold standard for platelet function assessment. The automated coagulation analyzer from Sysmex that performs LTA offers the advantage of being a walk-away technology. Recently, a new parameter "ADP-induced platelet aggregation level (APAL)" was developed to support the interpretation of results. APAL is calculated as a score from 0.0 to 10.0 based on platelet aggregation patterns with 1 and 10 µM adenosine diphosphate (ADP). Here, the basic performance of the newly developed APAL system and comparison with the maximum aggregation rate of ADP (ADP-MA) was evaluated. METHODS: The within-run precision was calculated by conducting five replicate analyses of the platelet-rich plasma (PRP) from healthy volunteers and 0.05 µM of cangrelor-spiked PRP. Cangrelor is a P2Y12 inhibitor that does not require liver CYP activation. The reference interval was calculated from the results of 67 healthy volunteers. The effect of the antiplatelet P2Y12 agent was evaluated using several concentrations of cangrelor. A comparative study was performed using 103 PRP samples with different levels of aggregation. Each test was analyzed with both APAL and ADP-MA. RESULTS: The percentage coefficient of variation in within-run precision was within 7% for APAL and 10 µM ADP-MA. Reference interval of APAL and 10 µM ADP-MA was 7.1 - 10.0 and 80.0 - 99.2%, respectively. APAL signifi-cantly decreased with the addition of 0.02 µM cangrelor, while 10 µM ADP-MA was barely affected. A significant correlation was observed between APAL and 10 µM ADP-MA (r = 0.94; p < 0.0001). CONCLUSIONS: The newly developed APAL system exhibited an acceptable performance. APAL score showed a good correlation with ADP-MA and was adequate to detect the weak effect of P2Y12 inhibitors. APAL is a new platelet aggregation scoring system with the potential to monitor the effects of P2Y12 inhibitor over a wide range.

Prognostic factors of premature closure of the ductus arteriosus in utero: a systematic literature review.

BACKGROUND: A number of case reports show various outcomes of premature closure of the ductus arteriosus in utero, including persistent pulmonary hypertension of the newborn and fetal or neonatal death; however, no study clarifies the clinical observations that are related to their prognoses. We aimed to clarify the prognostic factors of intrauterine ductal closure by a systematic literature review. Data sources We searched PubMed database (1975-2014) to identify case reports and studies on intrauterine closure of the ductus arteriosus, including maternal, fetal, and neonatal clinical information and their prognoses. RESULTS: We analysed the data of 116 patients from 39 articles. Of these, 12 (10.3%) died after birth or in utero. Fetal or neonatal death was significantly correlated with fetal hydrops (odds ratio=39.6, 95% confidence interval=4.6-47.8) and complete closure of the ductus arteriosus (odds ratio=5.5, 95% confidence interval=1.2-15.1). Persistent pulmonary hypertension was observed in 33 cases (28.4%), and was also correlated with fetal hydrops (odds ratio=4.2, 95% confidence interval=1.3-4.6) and complete closure of the ductus arteriosus (odds ratio=5.5, 95% confidence interval=1.6-6.0). Interestingly, maternal drug administration was not correlated with the risk of death and persistent pulmonary hypertension. CONCLUSIONS: Fetal hydrops and complete ductal closure are significant risk factors for both death and persistent pulmonary hypertension. Cardiac or neurological prognoses could be favourable if the patients overcome right heart failure during the perinatal period.

Cardiomyocyte differentiation from mouse embryonic stem cells using a simple and defined protocol.

BACKGROUND: Embryonic stem (ES) cells are pluripotent cells with the ability to differentiate to any cell type of the resident organism. In recent years, significant advances have been made in using these cells to obtain large numbers of cardiomyocyte (CM)-like cells for scientific research and clinical application. A vast number of protocols have emerged describing differentiation methods without the use of animal serum or extracts restrictive for use in a human clinical setting. These techniques follow a complicated procedure, which although successful, show a relatively varied yield among cell batches. RESULTS: We have designed a three-step differentiation protocol using defined reagents and a monolayer culture without feeder cells, avoiding embryoid body formation and multiple trypsin treatment, in which beating foci appeared as early as day 6 in in vitro differentiating conditions. Our results show a high yield of CM reaching approximately 60% of the differentiated cells after 13 days in vitro. CONCLUSIONS: We provide a fast, simple, reliable and reproducible protocol for inducing murine ES cells toward a CM-like phenotype comparable to available high-yield protocols, without the use of intermediate trypsinization/passage steps.

[Change in Serum Levels of New Hepatic Fibrosis Marker "Mac-2 Binding Protein Glycosylation isomer (M2BPGi)" in Patients with Chronic Hepatitis C during the Treatment of Pegylated Interferon and Ribavirin].

The sustained virological response (SVR) rate in the patients with HCV has currently reached to 90% by the progression of anti-viral therapy. However, several reports demonstrated that hepatocellular carcinoma develops even in the patients with SVR. It is widely accepted that liver fibrosis plays a pivotal role in hepatocellular carcinogenesis. Thus, an accurate staging for liver fibrosis is necessary to improve long-term prognosis of hepatitis C patients. Recently, Mac-2 binding protein glycosylation isomer (M2BPGi) was identified as a novel hepatic fibrosis marker. In the present study, we compared the value of M2BPGi in serum before and after the anti-viral therapy in hepatitis C patients. The value of M2BPGi in patients with F2, F3, or F4 stagings was significantly higher than that in F1 staging. Moreover, the value of M2BPGi significantly decreased after the treatment with pegylated interferon plus ribavirin similarly to other liver fibrosis-related markers. In addition, the value of M2BPGi in patients with SVR was significantly decreased after the anti-viral therapy (P < 0.0001). The reduction of M2BPGi in SVR patients was thought to reflect the improvement of liver fibrosis, in conjunction with the reduction of viral load, after the treatment. In conclusion, the measurement of M2BPGi in serum might be useful in monitoring the improvement of liver fibrosis by anti-viral therapy.

IL-23 protection against Plasmodium berghei infection in mice is partially dependent on IL-17 from macrophages.

Although IL-12 is believed to contribute to protective immune responses, the role played by IL-23 (a member of the IL-12 family) in malaria is elusive. Here, we show that IL-23 is produced during infection with Plasmodium berghei NK65. Mice deficient in IL-23 (p19KO) had higher parasitemia and died earlier than wild-type (WT) controls. Interestingly, p19KO mice had lower numbers of IL-17-producing splenic cells than their WT counterparts. Furthermore, mice deficient in IL-17 (17KO) suffered higher parasitemia than the WT controls, indicating that IL-23-mediated protection is dependent on induction of IL-17 during infection. We found that macrophages were responsible for IL-17 production in response to IL-23. We observed a striking reduction in splenic macrophages in the p19KO and 17KO mice, both of which became highly susceptible to infection. Thus, IL-17 appears to be crucial for maintenance of splenic macrophages. Adoptive transfer of macrophages into macrophage-depleted mice confirmed that macrophage-derived IL-17 is required for macrophage accumulation and parasite eradication in the recipient mice. We also found that IL-17 induces CCL2/7, which recruit macrophages. Our findings reveal a novel protective mechanism whereby IL-23, IL-17, and macrophages reduce the severity of infection with blood-stage malaria parasites.

[A case of small bowel cancer with positive peritoneal cytology and five-year recurrence-free survival].

Small bowel cancer is frequently detected at an advanced stage and its prognosis is poor. We report on a patient with small bowel cancer with positive peritoneal cytology who survived for 5 years without recurrence after surgery.The case involved a 73-year-old woman who had undergone partial resection of the small intestine and lymphadenectomy for a small bowel tumor with obstruction. Pathological examination confirmed papillary adenocarcinoma with partial serosal invasion. Ascites cytology indicated a class V tumor. Adjuvant chemotherapy with TS-1 was administered for 20 months, and the patient has survived without evidence of disease for over 5 years.In this case, it is possible that TS-1 chemotherapy was effective for prevention against small bowel cancer recurrence.Furthermore , peritoneal cytology in patients with small bowel cancer should be evaluated as a predictor of prognosis.

Impaired Relaxation in Induced Pluripotent Stem Cell-Derived Cardiomyocytes with Pathogenic TNNI3 Mutation of Pediatric Restrictive Cardiomyopathy.

BACKGROUND: Restrictive cardiomyopathy (RCM) is characterized by impaired diastolic function with preserved ventricular contraction. Several pathogenic variants in sarcomere genes, including TNNI3, are reported to cause Ca2+ hypersensitivity in cardiomyocytes in overexpression models; however, the pathophysiology of induced pluripotent stem cell (iPSC)-derived cardiomyocytes specific to a patient with RCM remains unknown. METHODS AND RESULTS: We established an iPSC line from a pediatric patient with RCM and a heterozygous TNNI3 missense variant, c.508C>T (p.Arg170Trp; R170W). We conducted genome editing via CRISPR/Cas9 technology to establish an isogenic correction line harboring wild type TNNI3 as well as a homozygous TNNI3-R170W. iPSCs were then differentiated to cardiomyocytes to compare their cellular physiological, structural, and transcriptomic features. Cardiomyocytes differentiated from heterozygous and homozygous TNNI3-R170W iPSC lines demonstrated impaired diastolic function in cell motion analyses as compared with that in cardiomyocytes derived from isogenic-corrected iPSCs and 3 independent healthy iPSC lines. The intracellular Ca2+ oscillation and immunocytochemistry of troponin I were not significantly affected in RCM-cardiomyocytes with either heterozygous or homozygous TNNI3-R170W. Electron microscopy showed that the myofibril and mitochondrial structures appeared to be unaffected. RNA sequencing revealed that pathways associated with cardiac muscle development and contraction, extracellular matrix-receptor interaction, and transforming growth factor-ß were altered in RCM-iPSC-derived cardiomyocytes. CONCLUSIONS: Patient-specific iPSC-derived cardiomyocytes could effectively represent the diastolic dysfunction of RCM. Myofibril structures including troponin I remained unaffected in the monolayer culture system, although gene expression profiles associated with cardiac muscle functions were altered.

Drastic shift from positive to negative estrogen effect on bone morphogenetic protein signaling in pulmonary arterial endothelial cells under hypoxia.

BACKGROUND: To investigate the possible role of sex hormones in the pathogenesis of pulmonary arterial hypertension (PAH), the effect of ß-estradiol (E2) on bone morphogenetic protein (BMP) signaling, a key signaling pathway involved in PAH, was studied in human pulmonary arterial endothelial cells (HPAEC). METHODS AND RESULTS: BMP signaling molecules, including BMP receptor, Smad1/5/8 and Id1, were studied in HPAEC under 1% O2 (hypoxia) and 21% O2 (normoxia) as well as the effect of hypoxia-inducible factor (HIF)-1α expression in the presence of E2 on BMP signaling. The effects of an estrogen receptor (ER) antagonist (ICI 182,780) and cycloheximide, and the interaction of ER with Smad or HIF-1α were also studied. In the presence of E2, BMP signaling was augmented under normoxia but suppressed under hypoxia. HIF-1α accumulation suppressed BMP signaling, whereas HIF-1α inhibition augmented signaling. These effects were cancelled by ICI 182,780. Moreover, binding between ER, HIF-1α and phosphorylated (p)-Smad1/5/8 proteins occurred only under hypoxia. On inhibition of de novo synthesis with cycloheximide, however, p-Smad1/5/8 expression was suppressed only under normoxia. CONCLUSIONS: The effects of E2 on BMP signaling in HPAEC altered depending on O2 concentration and different mechanisms may be involved. BMP and sex hormones may play an important role in PAH development.

A simple and novel method for RNA-seq library preparation of single cell cDNA analysis by hyperactive Tn5 transposase.

BACKGROUND: Deep sequencing of single cell-derived cDNAs offers novel insights into oncogenesis and embryogenesis. However, traditional library preparation for RNA-seq analysis requires multiple steps with consequent sample loss and stochastic variation at each step significantly affecting output. Thus, a simpler and better protocol is desirable. The recently developed hyperactive Tn5-mediated library preparation, which brings high quality libraries, is likely one of the solutions. RESULTS AND CONCLUSIONS: Here, we tested the applicability of hyperactive Tn5-mediated library preparation to deep sequencing of single cell cDNA, optimized the protocol, and compared it with the conventional method based on sonication. This new technique does not require any expensive or special equipment, which secures wider availability. A library was constructed from only 100 ng of cDNA, which enables the saving of precious specimens. Only a few steps of robust enzymatic reaction resulted in saved time, enabling more specimens to be prepared at once, and with a more reproducible size distribution among the different specimens. The obtained RNA-seq results were comparable to the conventional method. Thus, this Tn5-mediated preparation is applicable for anyone who aims to carry out deep sequencing for single cell cDNAs.