CSB327 Lecture 15 Summary

3 Pages
65 Views
Unlock Document

Department
Cell and Systems Biology
Course
CSB327H1
Professor
Maurice Ringuette
Semester
Fall

Description
Lecture 15 - Types of bone o Cortical bone (lamellar/compact) is dense, found in the shaft of long bones o Spongy bone (trabecular/cancellous) is lighter and less dense, consists of plates (trabeculae) - SIBLING family of small calcium binding glycoproteins that bind to integrin o Bone sialoprotein (BSP)  promote mineralization  Binding of HA to stretches of glutamic residues  Highly phosphorylated and sulfated  RFD integrin binding site (e.g., BSP is integrin binding protein)  High sialic acid content  Bone specific o Osteopontin (OPN)  block mineralization  Binding of HA to polyaspartic acid motif  Highly phosphorylated  RGD integrin binding site (e.g., OPN is integrin binding protein)  Broad tissue distribution o Expressed in tissues that undergo mineralization, but also found in other tissues (except BSP) - Composition of bone o 25% organic  90% type I collagen  10% BSP and OPN  5% cells (e.g., osteoblasts, osteocytes, osteoclasts, etc.) o 70% hydroxyapatite o 5% water - Temporal expression of bone-associated genes o Proliferation  Differentiation  Mineralization o BSP is expressed at the onset of mineralization  BSP interacts with α2 chain of type I collagen  BSP is localized in hole zone of collagen fibrils  HA is localized in hole zone too  BSP serve as a nucleator for HA crystal formation  BSP localized in Golgi and nascent bone matrix in vivo  BSP localized at sites of early mineralization in vitro o OPN has a biphasic expression before and after mineralization  OPN acts as an inhibitor of mineralization - Mineralization-competent matrix vesicles (MVs) o MVs secreted by osteoblasts (e.g., released into the matrix by exocytosis) o MVs can initiate HA crystal formation  NPP1 hydrolyzes NTP into NMP and PPi  PPi inhibits tissue mineralization  TNAP on vesicles hydrolyzes PPi into Pi (or PO )- 4  Type III Na+-dependent transporter bring extracellular phosphate molecules into the vesicle  Annexin bring extracellular calcium into the vesicle  Binds to collagens (CII and CX) in the hypertrophic zone  Phosphotidylserine bring calcium and phosphate in close proximity  During mineralizatoin, osteoblasts make MVs to begin HA formation within a confined space  When the MVs bind to collagen, they fall apart  They release and deposit nanocrystals into collagen fibrils  They set the stage for interaction of BSP within hole zone - Bone mineralization o Osteoblasts  Derived from mesenchymal cell precursors stimulated with BMP-2/4/7  Runx2 and Osx are master genes for osteoblast differentiation (e.g., osteogenesis)  Runx2 and Osx are transcription factors that promote pre-osteoblast  osteoblast  Runx2 is a master regulator of early osteogenesis o In Runx2 null mice, no osteoblast differentiation in endochondral and intramembranous ossification  Osx is a master regulator of late osteogenesis o In Osx null mice, no osteoblast differentiation and virtua
More Less

Related notes for CSB327H1

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit