Detection And Sequence Analysis Of Human Endogenous Retrovirus (HERV) In Human Astrocyte Cell Line And Patients Serum With Motor Neuron Disease

Human endogenous retrovirus (HERV) is derived from retrovirus which infected human germ line and integrated into human genome millions of years ago; represents about 8% of the human genome.Motor neuron diseases(MND)are a group of neurological disorders that selectively affect spinal anterior horn cells, motor neuron in the brain stem,cortex pyramidal cells and pyramidal tract. When the patient's syndrome appears and is finally diagnosed, the motor neurons basically have reached to the point which is incurable. Therefore, there is a need of a new biological disease maker which can help the clinic to diagnose quickly and take effective treatment in time.It is reported that the reverse transcriptase (RT) activity has increased in the serum and CSF of patients with amytrophic lateral sclerosis (ALS) (one of the most common motor neuron diseases).This result implies that RT might be related to the occurance and development of ALS but the source of RT has not been successfully discovered.1. Objectives and MethodsUtilize the serum of patients with ALS to extract nuclear acid; use Real time PCR to detect the existence and contents of HERV-K pol; employ the PCR amplification products to do TA cloning and then sequencing; analyze if there are mutations in RT gene pol and the important motif LPQG according to the sequences obtained. Conduct statistical analysis with all the data above accordingly to determine the relevance of HERV and MND.2. ResultReal Time PCR (relative quantitive method) was used to detect the HERV-K pol copy numbers of nuclear acid extracted from patients serum of the MND group and the nonMND group(include tumor group and control group). The result showed that the expression of HERV-K pol in the six tumor patients(tumor group) and 7 control patients(control group) is higher than the 20 MND patients(MND group).The relative amount of HERV-K pol gene in the MND group compared to the tumor group showed statistical significance P=0.001515 (P<0.01).Sequencing result analysis demostrated that different clonings derived from the same individual have diverce HERV-K pol gene mutation, that indicated that HERV-K pol sequence in the genome of one individual exist insertion polymorphism. In compare with the nonMND, HERV-K pol gene sequences clone from the PCR products of the MND group have more sequence mutations.Phylogenetic analysis dispalyed that most of the HERV-K sequences we obtained derived from the HML-2 and HML-3 family; very few from other families.3.ConclusionIt is possible that the HERV-K pol copy number in the 20 MND patients are originally low; the gene level avtivity of HERV-K pol might depend on the sequence mutation rather than increase of copy number. Henceforth, active expression of HERV-K sequences which belongs to the HML-2 and HML-3 family and the change of RT expression might be related with the neuron degeneration of MND.