Cystic Fibrosis is a multi-system disease marked by a monogenic condition. While Cystic Fibrosis is mostly a childhood condition, about 5% of adults are diagnosed with it. About 41% of Cystic Fibrosis patients are over the age of 18, and 13% are over the age of 30.

  • Gene Product: CFTR (cystic fibrosis transmembrane conductance regulator)
  •  Locus: 7q31.2
  • Gene Structure: ~ 250,000 bp; 27 exons.
  • mRNA: transcript for the gene is 6129 bp
  • Coding Sequence (CDS): 4443 bp
  • CFTR protein is 1480 Amino Acid; molecular weight of 168,173 Da

The CFTR protein is made up of five domains: 2 membrane-spanning domains (MSD1 & MSD2) that make up the chloride ion channel, 2 nucleotide-binding domains (NBD1 & NBD2) that bind and hydrolyze ATP, and 1 regulatory (R) domain.

chromosome 7
CFTR Mechanism

Six groups have been defined for CFTR gene mutations that influence development, different domains, and various functions. Class I (production) mutations truncate the protein, resulting in no active CFTR being made. Class II (processing) mutations are nontruncating and result in lower CFTR activity than natural. Class III (channel gating) mutations reduce chloride transfer by affecting the nucleotide binding domains (NBD1, NBD2).

The NBD and R domains are needed for the CFTR channel to open and close. Class IV (conductance) mutations change amino acids in transmembrane domains that make up the channel’s pore. Downregulation (Class C) mutations reduce the amount of functional CFTR produced. CFTR’s regulatory roles are affected by Class VI (regulatory) mutations. In general, CF cases in groups I, II, and III account for more than 85% of all cases.

The homozygous DF508 genotype is normally more serious than the other CFTR gene mutations. The severity of lung dysfunction varies among DF508 homozygotes, varying from moderate to extreme. The absence of a substantial connection between CFTR genotypes and phenotypes means that the phenotypic outcome is determined by other genes (modifier genes) and/or environmental factors.

How Cystic Fibrosis affects the body?

Comprehending the pathology of infectious illness necessitates an understanding of how the human body works in its natural state. To understand how CF affects the function of the lungs, pancreas, and other organs, we must first understand how the mechanisms affected by CF function in a healthy person. Although the most severe health issues for people with CF are chronic bronchial infections and gradual lung decline, the disease affects a variety of organ systems in the body, especially the exocrine glands.

The exocrine glands dump their enzymes and metabolites into ducts that lead out of the body or into empty organs like the intestine, unlike the endocrine glands (such as the pituitary, thyroid, and adrenal glands), which secrete their hormones directly into the bloodstream.

The Lungs and the Respiratory System

Clubbing is an enlargement or rounding of the tips of the fingers and toes that occurs in almost all individuals with CF as a result of lung disease. Substances produced in response to lung infections tend to penetrate the bloodstream and promote the growth of soft tissue at the base of the fingernails and toenails in some way.

The Pancreas and the Digestive System

Thick mucus can clog the pancreatic ducts in the majority of people with CF, particularly the smaller ones. Cysts and ultimately scar tissue develop as a result of the mucous plugs and the backup of enzymes in the pancreas. As a result, pancreatic enzymes are not able to enter the small intestine, allowing proteins and fats to pass through the body undigested.

Sweat Glands

Sweat is made up of a dilute solution of chemical electrolytes, mostly sodium and chloride, with minor concentrations of calcium and potassium. While sweating excessive salt is rarely life-threatening, excessive electrolyte loss can be dangerous in hot weather or when a person with CF engages in strenuous exercise or develops a fever. People with CF are more likely to get dehydrated or suffer from heat stroke than healthy people. People with CF should drink electrolyte solutions or eat salty foods to compensate for the salt imbalance, particularly if they have a fever or are exercising vigorously.

Reproductive Systems

The vas deferens is completely absent in most men with CF, a syndrome known as congenital bilateral absence of the vas deferens (CBAVD). Women with CF go through normal sexual development and growth, but their sexual maturation can start slower or take longer than healthy women. Women with CF can have regular sex lives, and the majority of them can become pregnant, but they should weigh the risks carefully before choosing to have children. People with CF have a higher risk of spontaneous abortions, premature pregnancies, and stillbirths, which is mostly due to their respiratory issues.

References:

  1. Nussbaum, R. L., McInnes, R. R., & Willard, H. F. (2016). THOMPSON & THOMPSON GENETICS IN MEDICINE, EIGHTH EDITION. In Elsevier (8th ed., Vol. 6).
Default image
clinicalsci

A tech enthusiast medical molecular technologist, biotechnologist and now also a blogger.

Articles: 66

Leave a Reply