Lecture 2: Granulocytes

Question 1

What are granulocytes?

Answer 1

White blood cells with cytoplasms filled with granules containing antimicrobial/immunomodulatory proteins

Question 2

What are the 2 stages of granulopoiesis?

Answer 2

Lineage Determination & Maturation

Question 3

What is the process of granulopoiesis?

Answer 3

Producing and maturing granulocytes in the bone marrow, through differentiation of HSC into myeloblast precursor cells, followed by other stages to form fully mature granulocytes

Question 4

What is the process of lineage determination, beginning with HSCs?

Answer 4

HSCs > common myeloid progenitors CMPs > granulocytes-monocyte progenitors GMPs stimulated by GM-CSF > multi-lobed granulocytes

Question 5

What is the purpose of G-CSF?

Answer 5

Stimulates GMP, making myeloblasts, which differentiate into promyelocytes, then forming fully mature granulocytes

Question 6

What are the 3 main transcription factors involved in lineage commitment of HSCs?

Answer 6

PU1, C/EBPs, and GATA-2

Question 7

What does PU1 consist of?

Answer 7

• N-terminal transactivation domain
• PEST domain, serves as activation sequence to recruit transcriptional enhancer proteins
• conserved ETS domain at the C-terminus

Question 8

How can PU1 be used to determine neutrophil maturity?

Answer 8

PU1 is highly detectable in the nucleus of neutrophil precursors, but absent during late maturation

Question 9

What is the result of deleting PU1 gene?

Answer 9

Hematopoietic defects including loss of development of myeloid and lymphoid cells

Question 10

What does PU1 do?

Answer 10

• Interacts with PU boxes in the genome to activate transcription of target genes
• Is expressed by myeloid and B lymphoid lineages, ETS domain mediated binding to DNA and interactions with other proteins

Question 11

What are C/EBPs?

Answer 11

A family of 6 CCAAT-enhancer-binding proteins

Are transcription factors that bind DNA to open up chromatin which induces gene expression

Question 12

What do C/EBPs consist of?

Answer 12

• Leucine zipper dimerisation domain at C terminus, to open sites of the genome for transcription
• A basic region

Question 13

What is the result of C/EBP knockout?

Answer 13

Loss of mature neutrophils, decrease in monocyte frequency, differentiation block in transition from CMP to GMP

Question 14

What cells are C/EBP epsilon found in?

Answer 14

Confined to granulocytic cells

Question 15

What is GATA-2 useful for?

Answer 15

Crucial for proliferation and maintenance of HSCs and multipotent progenitors

Question 16

What cells are GATA-1 expressed in?

Answer 16

Primitive and definitive erythroid cells, megakaryocytes, eosinophils, and mast cells

Question 17

How does GATA cross regulatory mechanisms work in erythrocytes?

Answer 17

GATA-1 controls expression of GATA-2 (and vice versa)

High levels of GATA-2 activates GATA-1 and induces a feedback loop to prevent GATA-2 transcription

Question 18

How many granule types are formed and in what order are they released ?

Answer 18

3 types, released backwards

Tertiary > secondary > primary