Question

Given the expression profile of CFTR (tissues in which it is normally expressed) in non-affected individuals and what you know about CFTR function and membrane transport, how would dysfunctional CFTR lead to each of the following common cystic fibrosis symptoms? Use proper terms and include specific information relevant to membrane transport in your explanations.

a.Thickened mucus of the lungs, pancreas, and GI tract

b.Increased bacterial infections of the lungs

c. Poor growth and malnutrition

Answer 1

CFTR ( Cystic Fibrosis Transmembrane Conductance Regulator) gene located on the chromosome 7 encodes 1480 amino acids produces CFTR protein, this protein acts as the channel on the membrane of cells associated with production of mucus, saliva, tears and digestive enzymes. the channel helps in the transport of negatively charged particles called as the chlorine ions in and out of the cells thus helps in maintainiong the water content in cells, but of the gene is mutated the balanced movement of the negative and positive ions across the membrance is disturbed and may lead to life threatning effects on pancreas, GIT and respiratory tract in case of infants it can cause serious complications the various symptoms associated with dysfunction of Cystc Fibrosis are like fatigue,chronic cough, thick and sticky mucus, inability of absorption of the nutrients from the intestines, abnormal levels of digestive enzymes etc.

a) In case of a normal individual with normal CFTR gene the mucus is produced by the cells as a lubricant and helps body tissues, also enzymes are produced properly for normal function but in case the CFTR gene undergo mutation the mucus production is disrupted and the channels are clogged becuse of abnormal CFTR protein, the most vital organs gets effected like lungs, pancreas and GI tract.In case of lungs the thick mucus causes the breathing very difficult and the thick mucus start getting accumulating in the lungs and becomes a favorite site for the growth of the bacteria and various other microbes.similarly the pancreatic enzyme release is obstructed and may lead to the inflammation of pancreas (pancraetitis). In case of GI tract the absorption of nutrients, vitamins is effected also the defecation of waste becomes difficult and cause other GI tract complications.

b) once the thick mucus gets accumulated in the lungs breating becomes difficult and passageways are blocked thus bacteria are trapped in the mucus thus coughing causes the blood in mucus and infections develop.

c) malnutrition is becasue the nutrients are not absorbed from the intestines and thus growth is poor.