CRISPR-mediated base editing in mice using cytosine deaminase base editor 4

BACKGROUND: Many human genetic diseases arise from point mutations. These genetic diseases can theoretically be corrected through gene therapy. However, gene therapy in clinical application is still far from mature. Nearly half of the pathogenic single-nucleotide polymorphisms (SNPs) are caused by G:C>A:T or T:A>C:G base changes and the ideal approaches to correct these mutations are base editing. These CRISPR-Cas9-mediated base editing does not leave any footprint in genome and does not require donor DNA sequences for homologous recombination. These base editing methods have been successfully applied to cultured mammalian cells with high precision and efficiency, but BE4 has not been confirmed in mice. Animal models are important for dissecting pathogenic mechanism of human genetic diseases and testing of base correction efficacy in vivo. Cytidine base editor BE4 is a newly developed version of cytidine base editing system that converts cytidine (C) to uridine (U). RESULTS: In this study, BE4 system was tested in cells to inactivate GFP gene and in mice to introduce single-base substitution that would lead to a stop codon in tyrosinase gene. High percentage albino coat-colored mice were obtained from black coat-colored donor zygotes after pronuclei microinjection. Sequencing results showed that expected base changes were obtained with high precision and efficiency (56.25%). There are no off-targeting events identified in predicted potential off-target sites. CONCLUSIONS: Results confirm BE4 system can work in vivo with high precision and efficacy, and has great potentials in clinic to repair human genetic mutations.

Epilepsy in Southeast Asia, how much have we closed the management gap in past two decades?

@#The last review on epilepsy in Southeast Asian (SEA) countries was reported in 1997. This review aimed to update the understanding of epilepsy management in this region over the past 23 years. There has been significant increase in the epidemiological studies which reported a prevalence of 4.3-7.7 per 1,000 populations in this region. Reversible aetiologies of epilepsy such as head injury, birth trauma, cerebrovascular disease, and intracranial infections (neurocysticercosis or meningoencephalitis) are still prevalent, with a surge in autoimmune encephalitis. There was a surge in genetic studies which suggest ethnic variation. Treatment gap is still high especially in the rural and less developed areas, and the availability and affordability of newer anti-epileptic drugs (AEDs) is still a major challenge in SEA. Alternative medicine is a common practice but varies among different ethnic groups. AEDs hypersensitivity especially on the association between HLA-B*1502 and carbamazepine-related severe cutaneous reaction had been extensively studied and proven in nearly all SEA countries. However, HLA-B*1502 screening is not widely available in SEA and the cost-effectiveness of the screening is questionable. Stigma and its psychosocial consequences are still a major concern despite enormous efforts to study the public attitudes towards epilepsy and change of epilepsy naming in a few countries. The number and complexity of epilepsy surgery are progressing, but it is still under-utilized in many SEA countries, related to cost, cultural perception and lack of facilities. More resources should also be channelled in training adequate number of epileptologists who can spearhead epilepsy care around the region, as well as public education and research in epilepsy. In conclusion, there is an increase in epilepsy research in this region, gradual increase in trained neurologists and facilities, and efforts to reduce the knowledge and treatment gap, but the epilepsy management gap is still a battle to fight.

Peripheral neuropathy induced by drinking water contaminated with low-dose arsenic in Myanmar

BACKGROUND@#More than 140 million people drink arsenic-contaminated groundwater. It is unknown how much arsenic exposure is necessary to cause neurological impairment. Here, we evaluate the relationship between neurological impairments and the arsenic concentration in drinking water (ACDW).@*PARTICIPANTS AND METHODS@#A cross-sectional study design was employed. We performed medical examinations of 1867 residents in seven villages in the Thabaung township in Myanmar. Medical examinations consisted of interviews regarding subjective neurological symptoms and objective neurological examinations of sensory disturbances. For subjective neurological symptoms, we ascertained the presence or absence of defects in smell, vision, taste, and hearing; the feeling of weakness; and chronic numbness or pain. For objective sensory disturbances, we examined defects in pain sensation, vibration sensation, and two-point discrimination. We analyzed the relationship between the subjective symptoms, objective sensory disturbances, and ACDW.@*RESULTS@#Residents with ACDW ≥ 10 parts per billion (ppb) had experienced a "feeling of weakness" and "chronic numbness or pain" significantly more often than those with ACDW  50 ppb). These data suggest a threshold for the occurrence of peripheral neuropathy due to arsenic exposure, and indicate that the arsenic concentration in drinking water should be less than 10 ppb to ensure human health.

Effectiveness, safety and acceptability of the method of visual inspection with acetic acid (VIA) and cryotherapy based single-visit approach to cervical cancer prevention (CCP) in Kungyangon Township, Yangon Region, Myanmar.

Cervical cancer is the second most frequent cancer occurring among the women in Myanmar. Being a preventable cancer, it is crucial to have an organized screening program in place that uses simple, practical and cost effective technology so as to ensure that the screening services have a wide coverage and it is universally accessible. The aim of this study is to fi nd out the effectiveness, safety and acceptability of the method of visual inspection with acetic acid (VIA) and cryotherapy based single-visit approach for use in cervical cancer prevention (CCP) programmes in Myanmar. The study is a descriptive community-based study conducted from July 2013 to October 2014. A well trained central CCP mobile team from Central Women’s Hospital (CWH) of the University of Medicine 1 visited Kungyangon Township fortnightly during the weekends to carry out the study. During the 6 visits undertaken by the team, 1,617 married women between the ages of 30 - 49 years were screened for cervical cancer using VIA method. The screening coverage achieved was 8.97%. The VIA tests were positive in 121 women and the screening positive rate was 7.5%. Cryotherapy was given to 119 eligible women after proper counseling. The treatment rate was 98.35%. Two women needed loop electrosurgical excision procedure (LEEP) surgery. Another two women had invasive cancer on screening. Watery vaginal discharge for 2 to 3 weeks after cryotherapy was the only symptoms reported at the time of one month follow-up. At the time of 1 year follow-up visit, the defaulter rate was 13.45% and 3 women had persistent VIA positive lesions. The overall cure rate was 97.09%. Twenty local basic health staff (BHS) were trained during screening visits of the Central CCP team. A local CCP team was also formed to sustain the screening program at the community level. All women that participated in the study were happy with the single-visit approach and they have been supported by their husbands in their efforts to obtain treatment. In addition, it was found that the women undergoing cryotherapy successfully adhered to home-care instructions prescribed by the CCP team. The study has shown that the screen and treat single-visit approach can be successfully implemented and expanded to other areas so that a universal coverage can be obtained to control cervical cancer in Myanmar.

Calcium and phosphate homeostasis among normal Myanmar people, patients with pathologic bone fractures and recurrent renal stones

The serum calcium, phosphaye, alkaline phosphatase and urinary exdretion of calcium and phosphate were measure to judge the homeostasis status among apparently healthy Myanmar, pathologic bone fractures and recurrent renal stones. The calcium and phosphorus homeostasis was found to be the same as in literature among apparently healthy Myanmar of various age groups ranging from 10-90 yr of both sexes. The values decreased with advancing age and a rise was found around menopause in females. The levels of serum and urinary calcium, phosphorus, and serum akaline phosphatase found in the pathologic bone fractures suggested that high risk due to low bone density and malformation of matrix plays a major role, instead of hyperparathyroidism, in causing the fractures. The cause of recurrent renal stones in the majority of the subjects with normocalcemia and normocalceuria were found to be due to low GFR.

Comparison of malaria situation in a forested foot-hill area of Bago division between monsoon and cool-dry season

During exploratory survey by Medical Entomology Research Division, Department of Medical Research to select areas for anopheline ecology studies, Tha-bye-wa village, Oktwin Township, Bago Division was found to have a very high malaria parasite rate and also high vectors density as well as a rich mosquito fauna. The results of survey carried out in momsoon season and in the cool/dry season were compared and the epidemiological situation discussed.

Preliminary report on the morphological variations of Anopheles (cellia) minimus adult females

Anopheles minimus is a common anopheline species in Myanmar, especially in the forested foot -hill areas. During routine survey many variations in adult morphology were noted. Iso-female lines were raised from wild-caught female and the morphological variations in F1 adults were studied. At the same time the identification of specimens was confirmed by detailed examination of larval skin slides. A guide for field workers on identification of An.minimus was also presented.

Anopheline mosquitoes of Myanmar. 3: Anopheles (cellia) Philippinensis Ludlow, 1902 & Anopheles (cellia) nivipes (Theobald), 1903 in Myanmar and their differentiating characters

Malaria workers in Myanmar have only recorded the prevalence of Anopheles philippinensis in the country and anopheles nivipes have not yet been identified in Myanmar. The Department of Medical Research (DMR) survey teams to Tha-bye-wa, Oktwin Township collected many specimen provisionally identified in the field as An. philippinensis. Iso-female lines were raised from wild caught female to preparelarval skin, pupal skin and adult specimens for detail morphological examination. The specimens collected from the forested foot-hill area of Tha-bye-wa was found to be An. nivipes, which was recorded for the first time in Myanmar. The distribution,seasonal prevalence, adult bionomics and larval habits for both species, as described by previous wprkers were compared with the observations of the DMR survey teams.

Malaria Situation in a Forested Foot-hill Area of Myanmar

Entomological survey was carried out during July 1987 in a forestedfoot hill teak plantation area Tha-bye-wa village, Oktwin Township, Pegu Division. At the same time, thick and thin blood films were taken and spleen rate determined in children. The parasite rate for children under 10 years of age was 66.7

(16/24) and the infant parasite rate was 50

(2/4). The spleen rate for children 2-9 years age group was found to be 88.2

(15/17). The anopheline fauna collected was mostly made up of An. dirus, An.minimus, An. tessalatus, An. minimus was found to have occysts and one An. vagus collected biting man had sporozoites in the salivary glands. Two species of mosquitoes were also recorded for the first time in Burma. The epidemiological pattern of malaria transmission in the area and possible methodologies for control in such areas are discussed.