Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells.
Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the 'conductance repertoire' being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors) consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations.
Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
Jolene
J
Atia
Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
Conor
C
McCloskey
Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
Anatoly S
AS
Shmygol
University of Warwick, Coventry, United Kingdom.
David A
DA
Rand
University of Warwick, Coventry, United Kingdom.
Hugo A
HA
van den Berg
Division of Reproductive Health, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
Andrew M
AM
Blanks
D000200:Action Potentials; D055592:Biophysical Phenomena; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D019295:Computational Biology; D003198:Computer Simulation; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D015640:Ion Channel Gating; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism; D016623:Ion Pumps / Q000235:genetics / Q000378:metabolism; D017136:Ion Transport; D007700:Kinetics; D008564:Membrane Potentials; D008954:Models, Biological; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D009215:Myometrium / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D007473:Ion Channels; D016623:Ion Pumps; D012333:RNA, Messenger; D002118:Calcium