Question

Part1:

Use the information from outside resources about HGPS (Hutchinson-Gilford-progeria-syndrome) to answer the questions below.

1. Explain why the lamin A mutation is classified as a dominant-negative mutation.

2. What treatment do scientists develop to ameliorate the symptoms of HGPS in fibroblasts?

3. How did scientists use CRISPR to treat progeria?

Part 2:

1. Define the following terms:

   1. LAP2

2. HP1

3. Tri-Me-K9

4. Cryptic splice site

5. Morpholino oligonucleotide

6. Adeno-associated virus 9 (AAV9)

7. CRISPR

1. Cas9

Answer 1

1.

• HGPS is Hutchinson-Gilford Progeria syndrome. This results in old age like characteristics.
• It is a genetic disorder (Autosomal dominant) observed in children, caused by mutation in LMNA gene.
• Dominant refers to dominant allelic effect. Negative mutation is described by loss of specific protein or parts of proteins causing loss of fuction.
• LMNA genes are responsible for providing instructions for generation proteins Lamins.
• Lamin protein functions in determining the shape of nucleus in a cell.
• In HGPS, the different form (dominant negative) of lamin protein called Progerin.
• This affects the nuclear structure and the heterochromatin. It causes stalling of replication forming DNA breaks, causing cell cycle and genomic instability, and reduced heterochromatin.
• Farnesylated progerin leads to rigidity in nuclear lamina.
• Progerin stimulates other proteins like Notch.
• These changes lead to alteration of dysfunction and exhaustion of stem cells.

2.

• TERT is telomerase reverse transcriptase. It has reverse transcriptase activity in telomerase (terminal transferase) gene.
• Telomerase is RNP (Ribonucleoprotein) Polymerase. It functions in maintaining telomere length. It extends the linear chromosome at 3’ end.
• This in turn is related to the age-related deterioration and conditions or cellular senescence.
• Premature aging may be caused by telomere shortening.
• TERT, as catalytic component of telomerase, can maintain the length of telomerase by addition of telomeric repeat TTAGGG.
• When TERT is turned off, telomerase deficiency will cause reduced telomere length or produce damaged telomere.
• When TERT is turned back, it can regain the telomere length due to reverse transcriptase activity.
• When the normal telomere is regained, the age-related conditions are reversed.
• Though it is observed that overexpression of TERT, may enhance lifespan and protect from metabolic decline, its use should be limited and specific to the cell types.
• Telomerase activity is associated with cells like reproductive cells, stem cells and certain activated lymphocytes. It is not usually expressed in normal somatic cells.
• Thus, this mechanism may be used in fibroblast as treatment for progeria.

3.

• CRISPR is Clustered Regulatory Interspaced Short Palindromic Repeats.
• CRISPR associated –Protein 9 nuclease (Cas-9) is used as a molecular tool for editing of genomes.
• It acts in a similar manner as genetic engineering or construction of GMO (genetically modified organism).
• CRISPR/ Cas9 system has components that help in their gene editing:

1. crRNA- guide RNA (g RNA) and sequence recognizing tracrRNA
2. tracrRNA- in stem-loop structure, bind (to be activated) to cRNA
3. Cas9-active form have nuclease, nick formation, single strand/double strand breaks, editing.
4. sgRNA-single guide RNA-with combination of other components

The defective gene may be replaced by "knock out" with normal gene.