Impact of a de novo variant (c.802A>C/+ inGNPTG) identified in STU 63 family
To study the impact of a de novo heterozygous variant (c.802A>C/+) in GNPTG gene identified in one family (STU 63), mRNA expression profile and lysosomal enzyme study was performed along with mucolipidosis screening test. All the members of the family including the affected proband and unaffected father, mother and sister screened, were found negative for mucolipidosis test. The activity of the enzymes studied in plasma was found to be well within the normal range (table 5).
To quantify mRNA, the CT data obtained was used to calculate ΔCT values (ΔCT = CT target – CT reference) that are normalized to the housekeeping β-actin gene for each of the target gene studied (GNPTAB , GNPTG and NAGPA ) and plotted in the figure 6. The data suggests that there is variability within the controls (father, mother and sister) and there is no obvious difference between the proband and the internal control group.
The 2^- ΔΔCT calculations were performed to check if the control data can be clubbed. The ΔΔCT value was obtained by subtracting the ΔCT of proband with ΔCT of control (ΔΔCT = ΔCT test sample – ΔCT control). Because of the variability, and smaller sample size, 2- ΔΔCT calculation and statistical analysis was not possible. Also averaging the control ΔCt values and comparing it with the respective gene expression value in the single proband would be misleading. However, the data suggests that there is no apparent differences in the expression of GNPTG ,GNPTAB and NAGPA genes between the proband and the controls.