Lasting Epigenetic Influence of Early-Life Adversity on the

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Lasting Epigenetic Influence of Early-Life
Adversity on the BDNF Gene

• Tania L. Roth, Farah D. Lubin, Adam J. Funk, J.
  David Sweatt
• Presented by Justin P. Smith

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Background

• Early life maltreatment
• Changes neural mechanisms
• Psych illnesses MAJOR DEPRESSION, schizophrenia,
  bi-polar disorder
• Stress-induced changes
• Neural plasticity in PFC and hippocampus
• BDNF protein levels

not a real baby
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Background cont.

• Epigenetics!
• Direct methylation of DNA
• Posttranslational modification of histones
• Either can or gene transcription
• Biochem view DNA methylation was a static process
  (consensus is changing)

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Animals

• Male and Female Long-Evans rats
• All behavior testing done during light period
• Food and water ad libitum

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Design

• Maltreatment vs Cross-foster care
• 30 min/day for one week (PN1-7)
• Gene Assays
• Tissue from PFC and Hippocampus collected PN8,
  PN30 and PN90
• Zebularine DNA methylation inhibitor
• Left lateral ventricle of maltreated adults (7
  days)
• Zebularine or Vehicle
• Maltreated females mated, pups cross-fostered
• Controls
• PN8, PFC and hippocampus isolated

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Maltreatment

• Limited nesting resources in unfamiliar
  environment to stress mothers
• Pups were stepped on, dropped, dragged, actively
  rejected, roughly handled
• Littermate controls exposed to caregiving
• 30 min of maltreatment, PN1-7

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Fig 1
Infants experienced an adverse caregiving
environment. (A) Qualitative assessment of the
percent occurrence of pup-directed behaviors in
the maltreatment condition indicates that pups
experienced predominately abusive behaviors,
which resulted in considerable audible pup
vocalization. (B) In sharp contrast, pups
experienced significant amounts of normal
maternal care behaviors in the cross-fostered
maternal care condition
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Maltreatment During Infancy Decreases BDNF
GeneExpression in the Adult PFC

• Assessed BDNF total mRNA levels (exon IX) PFC
  hippocampus of adult males and females
• Exposed to the maltreatment paradigm as neonates
• Suggests hippocampal ? was not exclusive to the
  experience of maltreatment, reflective of other
  variables
• exposure to new caretakers
• experience in a novel environment
• and/or removal from the biological mother and
  home cage

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Fig 2
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BDNF
BDNF gene contains nine 5 non-coding exons
(I-IXA), each linked to a unique promoter that
differentially splices to the common 3 coding
exon IX. The activity of each noncoding promoter
region dictates differential expression of
BDNF exon-specific transcripts, providing
tissue-specific and activity dependent regulation
of the BDNF gene across development and in
adulthood
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Infancy Maltreatment Elicits a Lasting Increase
inBDNF DNA Methylation in the PFC

• BDNF gene expression correlated with changes in
  BDNF DNA methylation
• Evaluated exon IV encompassing the transcription
  start site and (cAMP) response element
• epigenetic regulation of this region is gaining
  support for role in neural activity-dependent
  BDNF gene expression
• Evaluated exon IX, large CpG sites
• Exon IV and Exon IX mRNA transcripts ? during
  postnatal development in the cortex and
  hippocampus
• Dynamic methylation of exon IV suggested
  mechanism mediating BDNF gene expression during
  development and thus susceptible to environmental
  insults

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Fig 3
Maltreated groups only
Age
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Confirming methylation

• Direct bisulfite DNA sequencing PCR (BSP) on
  site-specific methylation of 12 CpG dinucleotides
  within the same region of exon IV screened by
  methylation specific real-time PCR (MSP)
• Significant increases in methylation across the
  region in adults with a history of maltreatment
  (Fig 4)

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Fig 4

cAMP response element site
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Deficits in BDNF Gene Expression inthe Adult PFC
Rescued by Treatment with a DNAMethylation
Inhibitor

• Infused zebularine, a DNA methylation inhibitor,
  left ventricle over 7 days
• Sufficient to ? methylation of BDNF exon IV DNA
  and rescue both BDNF exon IV mRNA total mRNA
  levels in adults with maltreatment history

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Fig 5
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Maltreated Zebularine no diff from normal
control
Fig 5
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BDNF DNA Methylation Patterns in the PFC
fromMaltreatment Are Perpetuated to the Next
Generation
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Fig 6
Females with a history of maltreatment display
aberrant maternal behavior toward their own
offspring
Theres your problem
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Fig 7

• A) Cross-fostering mal-offspring to a female with
  a history of normal infancy (Mal-Normal)? site 1
• B) Reverse methyl _at_ site 2
• C) Cross-fostering ? methyl but still ? over
  normal

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Fig 8

• Prepartum behavioral observations
• indicate that females with history of
  maltreatment displayed
• significantly more anxiety-related behaviors

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Conclusion

1. Infant maltreatment results in methylation of
   BDNF DNA through the lifespan to adulthood,
   reduced BDNF gene expression in the adult PFC
2. Altered epigenetic marks and gene expression in
   the adult can be rescued with chronic treatment
   of a DNA methylation inhibitor (zebularine)
3. Abused rats grow up and mistreat their own
   offspring and their offspring also have
   significant DNA methylation
4. Inability of cross-fostering to completely rescue
   CNS DNA methylation

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Thank you