Localized Elevation of Wall Shear Stress Is Linked to Recent Symptoms in Patients with Carotid Stenosis.

BACKGROUND: Estimation of symptomatic and asymptomatic carotid atherosclerosis differences can be the basis for prevention and management of carotid artery stenosis disease. In clinical practice, carotid plaque vulnerability is assessed only on the basis of luminal stenosis. However, the evolution of carotid plaque from an asymptomatic state to a symptomatic one is a complex process and the underlying hemodynamic mechanisms are unknown. We aimed to investigate the differences in hemodynamic parameters between patients with recently symptomatic carotid stenosis and asymptomatic ones. METHODS: Hemodynamic simulations were performed on 26 carotid plaques from 25 patients with carotid artery stenosis ≥50%, 16 of whom had recent cerebrovascular ischemic events. Using human-specific flow parameters and 3D reconstruction of carotid computed tomography angiography images, we assessed hemodynamic characteristics such as wall shear stress (WSS), time-averaged WSS (TAWSS), oscillatory shear index, and relative residence time (RRT) during the cardiac cycle in patients with and without symptoms. RESULTS: We found that symptomatic carotid stenosis patients had greater local TAWSS (99.59 ± 26.29 vs. 60.40 ± 20.46 dyn/cm2, p = 0.0007) and maximal WSS (116.65 ± 39.11 vs. 68.28 ± 23.67 dyn/cm2, p = 0.003), but lower RRT (0.019 ± 0.006 vs. 0.013 ± 0.069 s, p = 0.049), than asymptomatic patients, but this hemodynamic difference was not associated with carotid stenosis severity (p = 0.70). Patients with transient ischemic attack (TIA) or stroke had higher local TAWSS and WSSmax than patients with asymptomatic stenosis (p < 0.05). Subgroup analysis showed that there was no statistical difference in local hemodynamic variables between TIA and stroke patients with carotid artery stenosis. CONCLUSIONS: Patients with carotid artery stenosis are more likely to experience acute ischemic cerebrovascular accidents if they have higher WSS. Simultaneous assessment with hemodynamic parameters like WSS along with stenosis severity may aid risk stratification in patients with asymptomatic carotid artery stenosis.

CircCRIM1 Ameliorates Endothelial Cell Angiogenesis in Aging through the miR-455-3p/Twist1/VEGFR2 Signaling Axis.

Background: Aging leads to vascular endothelial cell senescence. Decreased expression of VEGFA and VEGFR2 plays a crucial role in impairing angiogenesis in senescent endothelial cells. Noncoding RNAs, including circular RNAs (circRNAs) and microRNAs (miRNAs), regulate endothelial cell proliferation, differentiation, apoptosis, and migration and participate in the occurrence and development of vascular diseases. However, the mechanism of noncoding RNAs in age-related vascular endothelial dysfunction remains unclear. Here, we aimed to identify the circRNA that is associated with VEGF/VEGFR2 signaling pathway activation in angiogenesis. Methods: Immunoblotting, quantitative reverse transcription-polymerase chain reaction (qRT-PCR), in vitro and in vivo experiments, luciferase assays, and chromatin immunoprecipitation followed by qRT-PCR (ChIP-qPCR) assays were performed to clarify the roles played by circCRIM1 in mouse aortic endothelial cell (MAEC) angiogenesis. Results: CircCRIM1 expression was downregulated in both an aging mouse model of lower limb ischemia in vivo and aging MAECs in vitro. Overexpressing circCRIM1 mediated through a plasmid or adeno-associated virus (AAV) reversed the downregulation of angiogenesis-related phenotype acquisition during aging. MiR-455-3p was confirmed to be a potential target of circCRIM1 through luciferase assays followed by RNA fluorescence in situ hybridization (FISH), which revealed the colocalization of circCRIM1 and miR-455-3p. CircCRIM1 was found to be a competitive endogenous RNA that sponged miR-455-3p and regulated angiogenesis-related phenotypes in MAECs. Furthermore, Twist1 was found to be downstream of miR-455-3p. A ChIP-qPCR assay showed that Twist1 promoted VEGFR2 expression by binding to the promoter region, playing a vital role in angiogenesis. Conclusions: Decreased expression of circCRIM1 impaired angiogenesis in aging via the miR-455-3p/Twist1/VEGFR2 axis. Our findings suggest that overexpression of circCRIM1 may be an effective therapeutic strategy for promoting ischemic lower limb blood flow recovery.

Circular RNA circGSE1 promotes angiogenesis in ageing mice by targeting the miR-323-5p/NRP1 axis.

Age is an important factor in many cardiovascular diseases, in which endothelial cells (ECs) play an important role. Circular RNAs (circRNAs) have been reported in many cardiovascular diseases, but their role in ageing EC-related angiogenesis is unclear. We aimed to identify a functional circRNA that regulates angiogenesis during ageing and explore its specific mechanism. In this study, we searched for differentially expressed circRNAs in old endothelial cells (OECs) and young endothelial cells (YECs) by circRNA sequencing and found that circGSE1 was significantly downregulated in OECs. Our study showed that circGSE1 could promote the proliferation, migration and tube formation of OECs in vitro. In a mouse model of femoral artery ligation and ischemia, circGSE1 promoted blood flow recovery and angiogenesis in the ischemic limbs of ageing mice. Mechanistically, we found that overexpressing circGSE1 reduced miR-323-5p expression, increased neuropilin-1 (NRP1) expression, and promoted proliferation, migration, and tube formation in OECs, while knocking down circGSE1 increased miR-323-5p expression, reduced NRP1 expression, and inhibited proliferation, migration, and tube formation in YECs. During EC ageing, circGSE1 may act through the miR-323-5p/NRP1 axis and promote endothelial angiogenesis in mice. Finally, the circGSE1/miR-323-5p/NRP1 axis could serve as a potential and promising therapeutic target for angiogenesis during ageing.

CircRNA FUT10 regulates the regenerative potential of aged skeletal muscle stem cells by targeting HOXA9.

Skeletal muscle is capable of repairing itself after injury to maintain the stability of its own tissue, but this ability declines with aging. Circular RNAs (circRNAs) are involved in cell aging. However, there is little research into their role and underlying mechanisms, especially in skeletal muscle stem cells (SkMSCs). In this study, we assessed circRNA FUT10 expression in aged and adult SkMSCs. We observed that circRNA FUT10 was upregulated in aged SkMSCs compared with that in adult SkMSCs. Furthermore, we identified putative miR-365-3p binding sites on circRNA FUT10, suggesting that this circRNA sponges miR-365a-3p. We also found that HOXA9 is a downstream target of miR-365a-3p and confirmed that miR-365a-3p can bind to circRNA FUT10 and the 3'-untranslated region of HOXA9 mRNA. This finding indicated that miR-365a-3p might serve as a "bridge" between circRNA FUT10 and HOXA9. Finally, we found that the circRNA FUT10/miR365a-3p/HOXA9 axis is involved in SkMSC aging. Collectively, our results show that the circRNA FUT10/miR365a-3p/HOXA9 axis is a promising therapeutic target and are expected to facilitate the development of therapeutic strategies to improve the prognosis of degenerative muscle disease.

Experience in the diagnosis and treatment of intravenous leiomyomatosis involving the inferior vena cava and/or right cardiac chambers.

OBJECTIVE: This study aimed to summarize our experience with the diagnosis and treatment of intravenous leiomyomatosis (IVL) involving the inferior vena cava (IVC) or right cardiac chambers. METHODS: This study retrospectively analyzed clinical data from 10 patients diagnosed with IVL involving the IVC or right cardiac chambers between May 2009 and October 2019 at one medical center. RESULTS: All patients were females aged 35 to 56 years (average, 46.8 years) with a history of uterine leiomyoma. Of these 10 patients, 8 manifested clinical symptoms and 2 were asymptomatic. Four were diagnosed with lesions involving the right cardiac chambers, four had lesions that extended into the suprahepatic IVC, and an additional two had lesions extending into the infrarenal IVC. All patients underwent surgery. Three of the four patients with extension into the right cardiac chambers underwent a two-stage operation, and an additional patient was managed with a one-stage operation. Patients who underwent a two-stage operation experienced less hemorrhaging and a shorter intensive care unit stay than the patient who underwent a one-stage operation. Six patients with intracaval extension alone underwent laparotomy, including four with a lesion extending into the suprahepatic IVC, under transesophageal echocardiography monitoring. Bilateral adnexectomy and ovariectomy were performed in seven patients, and unilateral adnexectomy and ovariectomy were performed in two patients; antiestrogen therapy was administered to two patients who retained a unilateral ovary and to one patient who retained bilateral ovaries. One patient suffered deep vein thrombosis in the left lower extremity after surgery that improved after treatment. All patients received conventional anticoagulant treatment postoperatively. All pathologic findings confirmed IVL, and the follow-up period ranged from 27 to 120 months (average, 57.5 months). Recurrence was not observed in the iliac vein or IVC, excluding one case of pelvic leiomyoma that recurred at one year postoperatively. CONCLUSIONS: IVL should be highly suspected when an IVC mass occurs in a patient with a history of uterine leiomyoma. Surgery is the gold standard treatment for IVL; a two-stage operation is more beneficial for patient recovery if the lesion exhibits intracardiac involvement, and transesophageal echocardiography is a helpful tool to monitor safety during surgical procedure for patients with a lesion invading the IVC above the level of the renal vein.

Impact of timely BCR-ABL1 monitoring before allogeneic stem cell transplantation among patients with BCR-ABL1-positive B-acute lymphoblastic leukemia

Background@#With the emergence of tyrosine kinase inhibitors and the incorporation of stringent measurable residual disease (MRD) monitoring, risk stratification for BCR-ABL1-positive acute lymphoblastic leukemia (ALL) patients has changed significantly. However, whether this monitoring can replace conventional risk factors in determining whether patients need allogeneic stem cell transplantation is still unclear. This study aimed to determine the impact of BCR-ABL1 monitoring on the outcome of patients with BCR-ABL1-positive ALL after allogeneic stem cell transplantation. @*Methods@#We retrospectively analyzed the survival outcome of patients with BCR-ABL1-positive ALL based on the quantification of BCR-ABL1 at 3 timepoints: the end of induction (timepoint 1), post-consolidation week 16 (timepoint 2), and the end of treatment for patients who were either transplant-eligible or non-transplant eligible (timepoint 3). @*Results@#From 2006 to 2018, a total of 96 patients newly diagnosed with BCR-ABL1-positive ALL were treated with chemotherapy and tyrosine kinase inhibitors. Thirty-eight (41.3%) patients achieved complete remission, and 33 patients underwent allogeneic stem cell transplantation. Our data showed that pre-transplant MRD monitoring by real-time quantitative polymerase chain reaction had the highest correlation with survival in patients with BCR-ABL1-positive ALL, especially for those who underwent allogeneic stem cell transplantation. @*Conclusion@#Patients without MRD pre-transplantation had superior survival compared with those who had MRD, and they had excellent long-term outcomes after allogeneic stem cell transplantation.

Impact of timely BCR-ABL1 monitoring before allogeneic stem cell transplantation among patients with BCR-ABL1-positive B-acute lymphoblastic leukemia

Background@#With the emergence of tyrosine kinase inhibitors and the incorporation of stringent measurable residual disease (MRD) monitoring, risk stratification for BCR-ABL1-positive acute lymphoblastic leukemia (ALL) patients has changed significantly. However, whether this monitoring can replace conventional risk factors in determining whether patients need allogeneic stem cell transplantation is still unclear. This study aimed to determine the impact of BCR-ABL1 monitoring on the outcome of patients with BCR-ABL1-positive ALL after allogeneic stem cell transplantation. @*Methods@#We retrospectively analyzed the survival outcome of patients with BCR-ABL1-positive ALL based on the quantification of BCR-ABL1 at 3 timepoints: the end of induction (timepoint 1), post-consolidation week 16 (timepoint 2), and the end of treatment for patients who were either transplant-eligible or non-transplant eligible (timepoint 3). @*Results@#From 2006 to 2018, a total of 96 patients newly diagnosed with BCR-ABL1-positive ALL were treated with chemotherapy and tyrosine kinase inhibitors. Thirty-eight (41.3%) patients achieved complete remission, and 33 patients underwent allogeneic stem cell transplantation. Our data showed that pre-transplant MRD monitoring by real-time quantitative polymerase chain reaction had the highest correlation with survival in patients with BCR-ABL1-positive ALL, especially for those who underwent allogeneic stem cell transplantation. @*Conclusion@#Patients without MRD pre-transplantation had superior survival compared with those who had MRD, and they had excellent long-term outcomes after allogeneic stem cell transplantation.

miR-25-3p promotes endothelial cell angiogenesis in aging mice via TULA-2/SYK/VEGFR-2 downregulation.

In aging, the regulation of angiogenesis is a dynamic and complex process. We aimed to identify and characterize microRNAs that regulate angiogenesis during aging. We showed that, in response to vascular endothelial senescence, microRNA-25-3p (miR-25-3p) plays the role of an angiogenic microRNA by targeting TULA-2 (T-cell ubiquitin ligand-2)/SYK (spleen tyrosine kinase)/VEGFR-2 (vascular endothelial growth factor receptor 2) signaling in vitro and in vivo. Mechanistic studies demonstrated that miR-25-3p inhibits a TULA-2/SYK/VEGFR-2 signaling pathway in endothelial cells. In old endothelial cells (OECs), upregulation of miR-25-3p inhibited the expression of TULA-2, which caused downregulation of the interaction between TULA-2 and SYK and increased phosphorylation of SYK Y323. The increased SYK Y323 phosphorylation level upregulated the phosphorylation of VEGFR-2 Y1175, which plays a vital role in angiogenesis, while miR-25-3p downregulation in YECs showed opposite effects. Finally, a salvage study showed that miR-25-3p upregulation promoted capillary regeneration and hindlimb blood flow recovery in aging mice with hindlimb ischemia. These findings suggest that miR-25-3p acts as an agonist of TULA-2/SYK/VEGFR-2 and mediates the endothelial cell angiogenesis response, which shows that the miR-25-3p/TULA-2 pathway may be potential therapeutic targets for angiogenesis during aging.

Strategy for treating vascular emergencies during the COVID-19 pandemic in China.

Coronavirus-caused pneumonia (COVID-19) broke out in December 2019. The virus soon proved to be extremely contagious and caused an international pandemic. Clinicians treating COVID-19 patients face considerable danger of occupational exposure because of the highly infectious nature of the virus, and precautions must be taken to prevent medical staff infections. This article lists important measures that may save the lives of patients and medical staff during the COVID-19 pandemic and help stop the transmission of COVID-19 on hospital grounds. The suggestions include establishing detailed infection control and prevention protocols in the operating room; expediting testing procedures and patient screening for COVID-19; using case-specific treatment planning for vascular patients with COVID-19, favoring minimally invasive methods; and establishing and reinforcing protective awareness of medical personnel.

TIM­3 inhibits PDGF­BB­induced atherogenic responses in human artery vascular smooth muscle cells.

Increasing evidence suggests that T­cell immunoglobulin and mucin domain 3 (TIM­3) displays anti­atherosclerotic effects, but its role in vascular smooth muscle cells (VSMCs) has not been reported. The present study aimed to investigate the function of TIM­3 and its roles in human artery VSMCs (HASMCs). A protein array was used to investigate the TIM­3 protein expression profile, which indicated that TIM­3 expression was increased in the serum of patients with lower extremity arteriosclerosis obliterans disease (LEAOD) compared with healthy individuals. Immunohistochemistry and western blotting of arterial tissue further revealed that TIM­3 expression was increased in LEAOD artery tissue compared with normal artery tissue. Additionally, platelet­derived growth factor­BB (PDGF­BB) displayed a positive correlation with TIM­3 expression in HASMCs. TIM­3 decreased the migration and proliferation of PDGF­BB­induced HASMCs, and anti­TIM­3 blocked the effects of TIM­3. The effect of TIM­3 on the proliferation and migration of HASMCs was further investigated using LV­TIM­3­transduced cells. The results revealed that TIM­3 also inhibited PDGF­BB­induced expression of the inflammatory factors interleukin­6 and tumor necrosis factor­α by suppressing NF­κB activation. In summary, the present study revealed that TIM­3 displayed a regulatory role during the PDGF­BB­induced inflammatory reaction in HASMCs, which indicated that TIM­3 may display anti­atherosclerotic effects.

miR-192-5p suppresses the progression of lung cancer bone metastasis by targeting TRIM44.

Lung cancer is the leading cause of cancer-related deaths worldwide, with 50-70% of patients suffering from bone metastasis. Accumulating evidence has demonstrated that miRNAs are involved in cell proliferation, migration, and invasion in malignancy, such as lung cancer bone metastasis. In the present study, we demonstrated that reduced miR-192-5p and increased TRIM44 levels were associated with the proliferation, migration and invasion of lung cancer. Furthermore, the potential functions of miR-192-5p were explored in A549 and NCI-H1299 cells. We found that miR-192-5p upregulation suppressed tumour behaviours in lung cancer cells. To further investigate whether miR-192-5p is associated with TRIM44, we used TargetScan software to predict the binding site between miR-192-5p and TRIM44. Luciferase activity assays were performed to verify this prediction. In addition, the significant role of miR-192-5p in negatively regulating TRIM44 expression was manifested by our research group. our results suggest that miR-192-5p inhibited the proliferation, migration and invasion of lung cancer through TRIM44.

Human Umbilical Cord-Derived Mesenchymal Stem Cells Relieve Hind Limb Ischemia by Promoting Angiogenesis in Mice.

Chronic critical limb ischemia (CLI) represents a clinical end stage of peripheral arterial disease. Many CLI patients are ineligible for conventional revascularization therapies; thus, it is urgent to explore an alternative strategy to rescue the ischemic limb. Recent stem cell studies have greatly developed the field of therapeutic angiogenesis, which aims to significantly improve the limb blood supply. In our study, bone marrow mesenchymal stem cells (BMMSCs) served as the control to evaluate the function of umbilical cord mesenchymal stem cells (UCMSCs) in enhancing angiogenesis. We compared gene expression between BMMSCs and UCMSCs, and a bioinformatics analysis indicated that both UCMSCs and BMMSCs could stimulate angiogenesis and angiogenesis-related factors were upregulated in UCMSCs. In vitro assays indicated that both BMMSCs and UCMSCs promoted human umbilical vein endothelial cell proliferation, migration, and tube formation, and the effects of UCMSCs were more obvious. Consistent with in vitro results, both UCMSCs and BMMSCs improved the limb blood supply in a mouse model of hind limb ischemia, in which UCMSCs promoted angiogenesis more significantly. Finally, we found that activation of ERK and PI3K-Akt pathways might be the mechanism by which UCMSCs promote angiogenesis. These results indicate that UCMSCs play an important role in therapeutic angiogenesis to improve limb blood perfusion.

An ectopic paraganglioma supplied by the subclavian artery in the right supraclavicular fossa.

Paragangliomas are rare and highly vascularized neuroendocrine tumors originating from neural crest-derived paraganglionic tissue surrounding the autonomic nerve. In this case, we report a nonfunctional paraganglioma located in the right supraclavicular fossa. Both computed tomography and paraffin-embedded sections diagnosed paraganglioma. The paraganglioma was presumed to be derived from the paraganglia of the right cervical parasympathetic nerve and primarily supplied by the right subclavian artery. Because of the abundant blood supply, we performed arterial embolization before the operation. This ectopic paraganglioma is considered a rare report of a paraganglioma supplied by the subclavian artery.

Sagittal Atlantoaxial Joint Inclination and Reduction Index Values for Diagnosis and Treatment of Irreducible Atlantoaxial Dislocation.

BACKGROUND: Irreducible atlantoaxial dislocation (IAAD) is a disorder of atlantoaxial joint instability with various causes. The diagnostic criteria for IAAD are variable. The diagnosis of IAAD is mainly based on preoperative and intraoperative traction results, as well as the physician's experience, with no relatively uniform guidelines for the selection of treatment. This study evaluates sagittal atlantoaxial joint inclination (SAAJI) and reduction index (RI) values for diagnosis and treatment of IAAD. MATERIALS AND METHODS: 24 IAAD patients treated in our hospital from January 2008 to July 2014 were retrospectively analysed. Patients included were 13 males and 11 females, with a mean age of 43 years. The various causes for IAAD were atlantoaxial transverse ligament rupture (n=3), old dens fracture (n=15), occipitalization of the atlas (n=6). The patients were divided into two groups. group A underwent anterior release with posterior reduction and fixation; Group B underwent posterior reduction and fixation; 12 healthy individuals served as controls. SAAJI and atlas-dens interval (ADI) values before and after traction were measured, and RI was calculated. Imaging data were analyzed. RESULTS: The mean SAAJI values were as follows: left, 5.6 ± 1.9° and right, 5.1 ± 2.1° in the control group; right, 39.5 ± 6.0° and left, 38.8 ± 5.8° in Group A; and right, 23.1 ± 7.0° and left, 23.9 ± 6.1° in Group B. There was no significant difference in the SAAJI values of the three groups (P < 0.05). The mean RIs in Groups A and B were 17.6 ± 9.3% and 34.4 ± 5.2%, respectively, and the difference was statistically significant (P < 0.05). There were obvious negative correlations between the SAAJI and RI values in Groups A and B. CONCLUSIONS: SAAJI and RI can be used as important imaging indicators to determine the reversibility of IAAD. If the RI value is >27.9% and SAAJI value is <32.5°, reduction and fixation can be achieved by the posterior approach alone; otherwise, a combination of anterior and posterior approaches would be necessary.

Lychee seed saponins improve cognitive function and ameliorate hippocampal neuronal injury in Alzheimer disease rat model induced by Aβ25-35 through AKT/GSK3β pathway / 中国药理学与毒理学杂志

OBJECTIVE Lychee seed, a famous traditional Chinese medicine, recently were reported to improve the learning and memory abilities in mice. However, it is still unclear whether lychee seed saponins (LSS) can improve the cognitive function and associated mechanisms. METHODS In present studies, we established the Alzheimer disease (AD) model by injecting Aβ25-35 into the lateral ventricle of rats. Then the spatial learning and memory abilities of LSS- treated rats were evaluated with the Morris water maze, meanwhile the protein expressions of AKT, GSK3β and Tau in the hippo?campal neuron were analyzed by immunohistochemistry and Western blotting. RESULTS The results showed LSS can improve the cognitive functions of AD rats through shortening the escape latency, increasing the number across the platform, platform quadrant dwell time and the percentage of the total distance run platform quadrant. The protein expression of AKT was significantly up-regulated and that of GSK3β and Tau were decreased remarkably in the hippocampal CA1 area. CONCLUSION Our study is the first to show that LSS significantly improve the cognitive function and prevent hippocampal neuronal injury of the rats with AD by activation of the PI3K/AKT/GSK3β signaling pathway, suggesting LSS may be developed into the nutrient supplement for the treatment of AD.

The prevalence and intensity of Amblyomma javanense infestation on Malayan pangolins (Manis javanica Desmarest) from Peninsular Malaysia.

A parasitological survey of 16 pangolins, confiscated from the Department of Wildlife and Nature Park Peninsular Malaysia (DWNP) at Kelantan and Pulau Pinang, Malaysia was conducted in 2011. Amblyomma javanense (family: Ixodidae) was the only ectoparasite found on the pangolins. The prevalence, intensity and life cycle of A. javanense were observed together with the respective pangolins' age and sex. It was found that 68.8% of the pangolins were infected, and significant difference, χ(2)(1, N=16)=4.02, p=0.05 were observed with males higher in infestation (88.9%) as compared to the females (42.9%). However, the mean intensity was higher on females (72) as compared to males (31.6). In addition, significant difference, χ(2) (2, N=16)=6.73, p=0.05 was recorded between adults and juveniles with juveniles found to be 100% infected as compared to adult (63.6%). Nevertheless, the mean intensity was slightly higher on adults (47) than juveniles (35). Adult ticks were found in higher numbers as compared to the nymph and larvae with number of male ticks higher (236) as compared to the females (53). Similarly, a high significant difference χ(2)(2, N=469)=203.47, p=0.05 was recorded in the composition of the tick's life stages with a higher number of adult ticks (61.6%) followed by nymph (30.3%) and larvae (8.1%). As such, the results of this study revealed a picture of the A. javanense life cycle which is related to the age and gender of the Malayan Pangolin.

Complex Loci in human and mouse genomes.

Mammalian genomes harbor a larger than expected number of complex loci, in which multiple genes are coupled by shared transcribed regions in antisense orientation and/or by bidirectional core promoters. To determine the incidence, functional significance, and evolutionary context of mammalian complex loci, we identified and characterized 5,248 cis-antisense pairs, 1,638 bidirectional promoters, and 1,153 chains of multiple cis-antisense and/or bidirectionally promoted pairs from 36,606 mouse transcriptional units (TUs), along with 6,141 cis-antisense pairs, 2,113 bidirectional promoters, and 1,480 chains from 42,887 human TUs. In both human and mouse, 25% of TUs resided in cis-antisense pairs, only 17% of which were conserved between the two organisms, indicating frequent species specificity of antisense gene arrangements. A sampling approach indicated that over 40% of all TUs might actually be in cis-antisense pairs, and that only a minority of these arrangements are likely to be conserved between human and mouse. Bidirectional promoters were characterized by variable transcriptional start sites and an identifiable midpoint at which overall sequence composition changed strand and the direction of transcriptional initiation switched. In microarray data covering a wide range of mouse tissues, genes in cis-antisense and bidirectionally promoted arrangement showed a higher probability of being coordinately expressed than random pairs of genes. In a case study on homeotic loci, we observed extensive transcription of nonconserved sequences on the noncoding strand, implying that the presence rather than the sequence of these transcripts is of functional importance. Complex loci are ubiquitous, host numerous nonconserved gene structures and lineage-specific exonification events, and may have a cis-regulatory impact on the member genes.