Altered synaptic connectivity and brain function in mice lacking microglial adapter protein Iba1

Pablo J. Lituma; Evan Woo; Bruce F. O’Hara; Pablo E. Castillo; Nicholas E.S. Sibinga; Sayan Nandi

doi:10.1073/pnas.2115539118

Altered synaptic connectivity and brain function in mice lacking microglial adapter protein Iba1

Pablo J. Lituma, Evan Woo, Bruce F. O’Hara, Pablo E. Castillo, Nicholas E.S. Sibinga, Sayan Nandi

Research output: Contribution to journal › Article › peer-review

25 Scopus citations

Abstract

Growing evidence indicates that microglia impact brain function by regulating synaptic pruning and formation as well as synaptic transmission and plasticity. Iba1 (ionized Ca⁺²-binding adapter protein 1), encoded by the Allograft inflammatory factor 1 (Aif1) gene, is an actin-interacting protein in microglia. Although Iba1 has long been used as a cellular marker for microglia, its functional role remains unknown. Here, we used global, Iba1-deficient (Aif1^-/-) mice to characterize microglial activity, synaptic function, and behavior. Microglial imaging in acute hippocampal slices and fixed tissues from juvenile mice revealed that Aif1^-/- microglia display reductions in ATP-induced motility and ramification, respectively. Biochemical assays further demonstrated that Aif1^-/-brain tissues exhibit an altered expression of microglial-enriched proteins associated with synaptic pruning. Consistent with these changes, juvenile Aif1^-/- mice displayed deficits in the excitatory synapse number and synaptic drive assessed by neuronal labeling and whole-cell patch-clamp recording in acute hippocampal slices. Unexpectedly, microglial synaptic engulfment capacity was diminished in juvenile Aif1^-/- mice. During early postnatal development, when synapse formation is a predominant event in the hippocampus, the excitatory synapse number was still reduced in Aif1^-/-mice. Together, these findings support an overall role of Iba1 in excitatory synaptic growth in juvenile mice. Lastly, postnatal synaptic deficits persisted in adulthood and correlated with significant behavioral changes in adult Aif1^-/- mice, which exhibited impairments in object recognition memory and social interaction. These results suggest that Iba1 critically contributes to microglial activity underlying essential neuroglia developmental processes that may deeply influence behavior.

Original language	English
Article number	e2115539118
Journal	Proceedings of the National Academy of Sciences of the United States of America
Volume	118
Issue number	46
DOIs	https://doi.org/10.1073/pnas.2115539118
State	Published - Nov 16 2021

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We thank Dr. David Julius of University of California San Francisco for the P2RY12 antibody. We thank Dr. Kostantin Dobrenis, Kevin Fisher, and Vladimir Mudragel of Einstein Neural Cell Engineering and Imaging Core supported by the Rose F. Kennedy Intellectual and Developmental Disabilities Research Center for technical advice and acknowledge support from the NIH shared instrument grant S10OD025295 to Dr. Kostantin Dobre-nis. We thank Dr. Derek M. Huffman and Zunju Hu of the Healthy Aging Physiology Core, the Einstein and Deann Hopkins of Rodent Behavior Core, and the University of Kentucky for assistance with behavioral analyses; Dr. Pramela-devi Chinnasamy and Smitha Jayakumar for assistance with mouse breeding; Kayla Oriyomi and Grace Tremonti for assistance with Sholl analyses; and the members of the Castillo Laboratory for providing critique of this work. This work was supported by NIH grants R21 NS116480 and R21 MH124294 and the Einstein Nathan Shock Center P&F core service award to S.N.; R01 HL128066 and R01 HL133861 to N.E.S.S.; R01 MH125772, R01 MH116673, and R01 NS113600 to P.E.C.; and a Ruth L. Kirschstein National Research Service Award Fellowship F31MH109267 to P.J.L.

Funding Information:
We thank Dr. David Julius of University of California San Francisco for the P2RY12 antibody. We thank Dr. Kostantin Dobrenis, Kevin Fisher, and Vladimir Mudragel of Einstein Neural Cell Engineering and Imaging Core supported by the Rose F. Kennedy Intellectual and Developmental Disabilities Research Center for technical advice and acknowledge support from the NIH shared instrument grant S10OD025295 to Dr. Kostantin Dobrenis. We thank Dr. Derek M. Huffman and Zunju Hu of the Healthy Aging Physiology Core, the Einstein and Deann Hopkins of Rodent Behavior Core, and the University of Kentucky for assistance with behavioral analyses; Dr. Prameladevi Chinnasamy and Smitha Jayakumar for assistance with mouse breeding; Kayla Oriyomi and Grace Tremonti for assistance with Sholl analyses; and the members of the Castillo Laboratory for providing critique of this work. This work was supported by NIH grants R21 NS116480 and R21 MH124294 and the Einstein Nathan Shock Center P&F core service award to S.N.; R01 HL128066 and R01 HL133861 to N.E.S.S.; R01 MH125772, R01 MH116673, and R01 NS113600 to P.E.C.; and a Ruth L. Kirschstein National Research Service Award Fellowship F31MH109267 to P.J.L.

Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.

Keywords

behavior
microglia
synapse

ASJC Scopus subject areas

General

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10.1073/pnas.2115539118

Cite this

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title = "Altered synaptic connectivity and brain function in mice lacking microglial adapter protein Iba1",

abstract = "Growing evidence indicates that microglia impact brain function by regulating synaptic pruning and formation as well as synaptic transmission and plasticity. Iba1 (ionized Ca+2-binding adapter protein 1), encoded by the Allograft inflammatory factor 1 (Aif1) gene, is an actin-interacting protein in microglia. Although Iba1 has long been used as a cellular marker for microglia, its functional role remains unknown. Here, we used global, Iba1-deficient (Aif1-/-) mice to characterize microglial activity, synaptic function, and behavior. Microglial imaging in acute hippocampal slices and fixed tissues from juvenile mice revealed that Aif1-/- microglia display reductions in ATP-induced motility and ramification, respectively. Biochemical assays further demonstrated that Aif1-/- brain tissues exhibit an altered expression of microglial-enriched proteins associated with synaptic pruning. Consistent with these changes, juvenile Aif1-/- mice displayed deficits in the excitatory synapse number and synaptic drive assessed by neuronal labeling and whole-cell patch-clamp recording in acute hippocampal slices. Unexpectedly, microglial synaptic engulfment capacity was diminished in juvenile Aif1-/- mice. During early postnatal development, when synapse formation is a predominant event in the hippocampus, the excitatory synapse number was still reduced in Aif1-/- mice. Together, these findings support an overall role of Iba1 in excitatory synaptic growth in juvenile mice. Lastly, postnatal synaptic deficits persisted in adulthood and correlated with significant behavioral changes in adult Aif1-/- mice, which exhibited impairments in object recognition memory and social interaction. These results suggest that Iba1 critically contributes to microglial activity underlying essential neuroglia developmental processes that may deeply influence behavior.",

keywords = "behavior, microglia, synapse",

author = "Lituma, {Pablo J.} and Evan Woo and O{\textquoteright}Hara, {Bruce F.} and Castillo, {Pablo E.} and Sibinga, {Nicholas E.S.} and Sayan Nandi",

note = "Funding Information: ACKNOWLEDGMENTS. We thank Dr. David Julius of University of California San Francisco for the P2RY12 antibody. We thank Dr. Kostantin Dobrenis, Kevin Fisher, and Vladimir Mudragel of Einstein Neural Cell Engineering and Imaging Core supported by the Rose F. Kennedy Intellectual and Developmental Disabilities Research Center for technical advice and acknowledge support from the NIH shared instrument grant S10OD025295 to Dr. Kostantin Dobre-nis. We thank Dr. Derek M. Huffman and Zunju Hu of the Healthy Aging Physiology Core, the Einstein and Deann Hopkins of Rodent Behavior Core, and the University of Kentucky for assistance with behavioral analyses; Dr. Pramela-devi Chinnasamy and Smitha Jayakumar for assistance with mouse breeding; Kayla Oriyomi and Grace Tremonti for assistance with Sholl analyses; and the members of the Castillo Laboratory for providing critique of this work. This work was supported by NIH grants R21 NS116480 and R21 MH124294 and the Einstein Nathan Shock Center P&F core service award to S.N.; R01 HL128066 and R01 HL133861 to N.E.S.S.; R01 MH125772, R01 MH116673, and R01 NS113600 to P.E.C.; and a Ruth L. Kirschstein National Research Service Award Fellowship F31MH109267 to P.J.L. Funding Information: We thank Dr. David Julius of University of California San Francisco for the P2RY12 antibody. We thank Dr. Kostantin Dobrenis, Kevin Fisher, and Vladimir Mudragel of Einstein Neural Cell Engineering and Imaging Core supported by the Rose F. Kennedy Intellectual and Developmental Disabilities Research Center for technical advice and acknowledge support from the NIH shared instrument grant S10OD025295 to Dr. Kostantin Dobrenis. We thank Dr. Derek M. Huffman and Zunju Hu of the Healthy Aging Physiology Core, the Einstein and Deann Hopkins of Rodent Behavior Core, and the University of Kentucky for assistance with behavioral analyses; Dr. Prameladevi Chinnasamy and Smitha Jayakumar for assistance with mouse breeding; Kayla Oriyomi and Grace Tremonti for assistance with Sholl analyses; and the members of the Castillo Laboratory for providing critique of this work. This work was supported by NIH grants R21 NS116480 and R21 MH124294 and the Einstein Nathan Shock Center P&F core service award to S.N.; R01 HL128066 and R01 HL133861 to N.E.S.S.; R01 MH125772, R01 MH116673, and R01 NS113600 to P.E.C.; and a Ruth L. Kirschstein National Research Service Award Fellowship F31MH109267 to P.J.L. Publisher Copyright: {\textcopyright} 2021 National Academy of Sciences. All rights reserved.",

year = "2021",

month = nov,

day = "16",

doi = "10.1073/pnas.2115539118",

language = "English",

volume = "118",

number = "46",

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TY - JOUR

T1 - Altered synaptic connectivity and brain function in mice lacking microglial adapter protein Iba1

AU - Lituma, Pablo J.

AU - Woo, Evan

AU - O’Hara, Bruce F.

AU - Castillo, Pablo E.

AU - Sibinga, Nicholas E.S.

AU - Nandi, Sayan

N1 - Funding Information: ACKNOWLEDGMENTS. We thank Dr. David Julius of University of California San Francisco for the P2RY12 antibody. We thank Dr. Kostantin Dobrenis, Kevin Fisher, and Vladimir Mudragel of Einstein Neural Cell Engineering and Imaging Core supported by the Rose F. Kennedy Intellectual and Developmental Disabilities Research Center for technical advice and acknowledge support from the NIH shared instrument grant S10OD025295 to Dr. Kostantin Dobre-nis. We thank Dr. Derek M. Huffman and Zunju Hu of the Healthy Aging Physiology Core, the Einstein and Deann Hopkins of Rodent Behavior Core, and the University of Kentucky for assistance with behavioral analyses; Dr. Pramela-devi Chinnasamy and Smitha Jayakumar for assistance with mouse breeding; Kayla Oriyomi and Grace Tremonti for assistance with Sholl analyses; and the members of the Castillo Laboratory for providing critique of this work. This work was supported by NIH grants R21 NS116480 and R21 MH124294 and the Einstein Nathan Shock Center P&F core service award to S.N.; R01 HL128066 and R01 HL133861 to N.E.S.S.; R01 MH125772, R01 MH116673, and R01 NS113600 to P.E.C.; and a Ruth L. Kirschstein National Research Service Award Fellowship F31MH109267 to P.J.L. Funding Information: We thank Dr. David Julius of University of California San Francisco for the P2RY12 antibody. We thank Dr. Kostantin Dobrenis, Kevin Fisher, and Vladimir Mudragel of Einstein Neural Cell Engineering and Imaging Core supported by the Rose F. Kennedy Intellectual and Developmental Disabilities Research Center for technical advice and acknowledge support from the NIH shared instrument grant S10OD025295 to Dr. Kostantin Dobrenis. We thank Dr. Derek M. Huffman and Zunju Hu of the Healthy Aging Physiology Core, the Einstein and Deann Hopkins of Rodent Behavior Core, and the University of Kentucky for assistance with behavioral analyses; Dr. Prameladevi Chinnasamy and Smitha Jayakumar for assistance with mouse breeding; Kayla Oriyomi and Grace Tremonti for assistance with Sholl analyses; and the members of the Castillo Laboratory for providing critique of this work. This work was supported by NIH grants R21 NS116480 and R21 MH124294 and the Einstein Nathan Shock Center P&F core service award to S.N.; R01 HL128066 and R01 HL133861 to N.E.S.S.; R01 MH125772, R01 MH116673, and R01 NS113600 to P.E.C.; and a Ruth L. Kirschstein National Research Service Award Fellowship F31MH109267 to P.J.L. Publisher Copyright: © 2021 National Academy of Sciences. All rights reserved.

PY - 2021/11/16

Y1 - 2021/11/16

N2 - Growing evidence indicates that microglia impact brain function by regulating synaptic pruning and formation as well as synaptic transmission and plasticity. Iba1 (ionized Ca+2-binding adapter protein 1), encoded by the Allograft inflammatory factor 1 (Aif1) gene, is an actin-interacting protein in microglia. Although Iba1 has long been used as a cellular marker for microglia, its functional role remains unknown. Here, we used global, Iba1-deficient (Aif1-/-) mice to characterize microglial activity, synaptic function, and behavior. Microglial imaging in acute hippocampal slices and fixed tissues from juvenile mice revealed that Aif1-/- microglia display reductions in ATP-induced motility and ramification, respectively. Biochemical assays further demonstrated that Aif1-/- brain tissues exhibit an altered expression of microglial-enriched proteins associated with synaptic pruning. Consistent with these changes, juvenile Aif1-/- mice displayed deficits in the excitatory synapse number and synaptic drive assessed by neuronal labeling and whole-cell patch-clamp recording in acute hippocampal slices. Unexpectedly, microglial synaptic engulfment capacity was diminished in juvenile Aif1-/- mice. During early postnatal development, when synapse formation is a predominant event in the hippocampus, the excitatory synapse number was still reduced in Aif1-/- mice. Together, these findings support an overall role of Iba1 in excitatory synaptic growth in juvenile mice. Lastly, postnatal synaptic deficits persisted in adulthood and correlated with significant behavioral changes in adult Aif1-/- mice, which exhibited impairments in object recognition memory and social interaction. These results suggest that Iba1 critically contributes to microglial activity underlying essential neuroglia developmental processes that may deeply influence behavior.

AB - Growing evidence indicates that microglia impact brain function by regulating synaptic pruning and formation as well as synaptic transmission and plasticity. Iba1 (ionized Ca+2-binding adapter protein 1), encoded by the Allograft inflammatory factor 1 (Aif1) gene, is an actin-interacting protein in microglia. Although Iba1 has long been used as a cellular marker for microglia, its functional role remains unknown. Here, we used global, Iba1-deficient (Aif1-/-) mice to characterize microglial activity, synaptic function, and behavior. Microglial imaging in acute hippocampal slices and fixed tissues from juvenile mice revealed that Aif1-/- microglia display reductions in ATP-induced motility and ramification, respectively. Biochemical assays further demonstrated that Aif1-/- brain tissues exhibit an altered expression of microglial-enriched proteins associated with synaptic pruning. Consistent with these changes, juvenile Aif1-/- mice displayed deficits in the excitatory synapse number and synaptic drive assessed by neuronal labeling and whole-cell patch-clamp recording in acute hippocampal slices. Unexpectedly, microglial synaptic engulfment capacity was diminished in juvenile Aif1-/- mice. During early postnatal development, when synapse formation is a predominant event in the hippocampus, the excitatory synapse number was still reduced in Aif1-/- mice. Together, these findings support an overall role of Iba1 in excitatory synaptic growth in juvenile mice. Lastly, postnatal synaptic deficits persisted in adulthood and correlated with significant behavioral changes in adult Aif1-/- mice, which exhibited impairments in object recognition memory and social interaction. These results suggest that Iba1 critically contributes to microglial activity underlying essential neuroglia developmental processes that may deeply influence behavior.

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KW - microglia

KW - synapse

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Altered synaptic connectivity and brain function in mice lacking microglial adapter protein Iba1

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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