h-channels contribute to divergent electrophysiological properties of supragranular pyramidal neurons in human versus mouse cerebral cortex

Abstract

24Gene expression studies suggest that differential ion channel expression 25 contributes to differences in rodent versus human neuronal physiology. We 26 tested whether h-channels more prominently contribute to the physiological 27 properties of human compared to mouse supragranular pyramidal neurons. 28Single cell/nucleus RNA sequencing revealed ubiquitous HCN1-subunit 29 expression in excitatory neurons in human, but not mouse supragranular layers. 30Using patch-clamp recordings, we found stronger h-channel-related membrane 31properties in supragranular pyramidal neurons in human temporal cortex, 32 compared to mouse supragranular pyramidal neurons in temporal association 33 area. The magnitude of these differences depended upon cortical depth and was 34 largest in pyramidal neurons in deep L3. Additionally, pharmacologically blocking 35 h-channels produced a larger change in membrane properties in human 36 compared to mouse neurons. Finally, using biophysical modeling, we provided 37 evidence that h-channels promote the transfer of theta frequencies from dendrite-38 to-soma in human L3 pyramidal neurons. Thus, h-channels contribute to 39 between-species differences in a fundamental neuronal property. 40 41 integration of synaptic input that is most pronounced in deep L3 pyramidal 88 neurons of human temporal cortex, which may generally represent an important 89 evolutionary adaptation for very large pyramidal neurons in the human neocortex. 90 Experimental Procedures 91Human surgical specimens 92Surgical specimens were obtained from local hospitals (Harborview Medical 94 in collaboration with local neurosurgeons. All patients provided informed consent 95 and experimental procedures were approved by hospital institute review boards 96 before commencing the study. The bulk of data included in this study were 97 obtained from tissue from 10 patients with temporal lobe epilepsy with a mean 98 age of 38.10 ± 15.67. Four patients were male and 6 were female. Additionally, 99 data were obtained from tissue from one patient who had undergone deep tumor 100 resection from the temporal lobe. Tissue obtained from surgery was distal to the 101 core pathological tissue and was deemed not to be of diagnostic value. 102Specimens were placed in a sterile container filled with an artificial cerebral 103 spinal fluid (aCSF) composed of (in mM): 92 with N-methyl-D-glucamine 104 (NMDG), 2.5 KCl, 1.25 NaH 2 PO 4 , 30 NaHCO 3 , 20 4-(2-hydroxyethyl)-1-105 piperazineethanesulfonic acid (HEPES), 25 glucose, 2 thiourea, 5 Na-ascorbate, 1063 Na-pyruvate, 0.5 CaCl 2 ·4H 2 O and 10 MgSO 4 ·7H 2 O. The pH of the NMDG 107 aCSF was titrated to pH 7.3-7.4 with concentrated hydrochloric acid and the 108 osmolality was 300-305 mOsmoles/Kg. The solution was pre-chilled to 2-4°C 109 and thoroughly bubbled with carbogen (95% O 2 /5% CO 2 ) prior to collection. 110 Surgical specimens were quickly transported from the surgical site to the 111 laboratory while continuously bubbled with carbogen (transportation time: 10-40 112 minutes). 113 Acute br...

Investigating microglia-neuron crosstalk by characterizing microglial contamination in human and mouse Patch-seq datasets

“…To help put these associations in context, microglial contamination explained 5.2% of the cell-to-cell variation in input resistance values among human FREM3 pyramidal cells. However, this value is similar to the variance in input resistance explained by the depth of the recorded neuron from the pial surface, 5.1%, noted previously to be a major biological factor distinguishing human superficial pyramidal cells from one another (Berg et al, 2021; Kalmbach et al, 2018; Moradi Chameh et al, 2021).…”

“…For example, the more contaminated cell had a lower input resistance (96 vs 167 MOhms), greater rheobase (110 vs 70 pA), a more depolarized resting membrane potential (-67.8 vs -70.6 mV), and more depolarized minimum voltage following an action potential (i.e., AP trough voltage, -42.8 vs -45.9 mV) than the less contaminated cell, among other differences. We note that these differences, while striking, are within the expected ranges of variability for these cells (Kalmbach et al, 2018;Moradi Chameh et al, 2021) and that the original electrophysiological datasets have undergone strict quality control (Berg et al, 2021). Across human FREM3 pyramidal cells, we also saw that higher microglial contamination scores were associated with lower input resistances (Figure 4A, Pearson's R = -0.22 , p = 0.011) and more depolarized action potential through voltages (Figure 4B, left, Pearson's R = 0.17, p = 0.047).…”

Conserved cell types with divergent features between human and mouse cortex

“…A major evolutionary feature of human cortical architecture is the expansion of supragranular layers compared to other mammals, and morphological and physiological properties of pyramidal neurons vary across layers 2 and 3 of human temporal cortex 40,41 . In that light, it was surprising to find only three main excitatory clusters in human cortical layers 2 and 3.…”

The timescale and magnitude of 1/f aperiodic activity decrease with cortical depth in humans, macaques, and mice

“…Secondly, the density of h-channels on the dendrites of layer 5 cortical pyramidal cells increases with distance on the apical trunk from the soma (Harnett et al, 2015; Kole et al, 2006), mirroring the smooth increase in 1/f slope from deep to superficial cortex. Additionally, human supragranular cells exhibit higher densities of h-channels when compared to rodents (Beaulieu-Laroche et al, 2018; Kalmbach et al, 2018); this may explain why the correlation between 1/f slope and depth was stronger in primates than mice. Alternatively, our effects could be due to biophysical differences across cortical layers.…”