發育中NRG1變異小鼠的多巴胺纖維，迦瑪胺基丁酸細胞和doublecortin在額腦區域表現的改變

Abstract

Neuregulin1(NRG1，神經調節素1)的功能為調節發育及細胞遷移，且nrg1 gene的變異可能會導致精神分裂症。NRG1 mutant mice的過動、認知行為異常和精神經分裂症(schizophrenia)病人症狀類似，因此可用來做研究精神分裂症病因的動物模式。此疾病成因可能因為基因、發育、神經傳導物質發生異常所造成。目前已知精神分裂症病人前額葉皮質神經傳導物質分泌異常。本篇研究為利用尼氏染色法及免疫化學染色比較四週、八週NRG1變異小鼠(△TM+/-)及野生型小鼠胼胝體的型態及額腦區域內蛋白質的表現，以探討NRG1變異小鼠行為異常背後的可能機制。 我們發現 1.胼胝體：四週和八週NRG1變異小鼠胼胝體長度及寬度較野生型小鼠無顯著差異，但在駢胝體面積四週NRG1變異小鼠較野生型小鼠下降約23％，八週NRG1變異小鼠和野生型小鼠相較無顯著差異。 2.扣帶皮質 (i)扣帶皮質1的L2/3： 八週NRG1變異小鼠tyrosine hydroxylase (TH)纖維密度較野生型上升73％，四週NRG1變異小鼠和野生型小鼠相較無顯著差異。四週和八週NRG1變異小鼠GAD67細胞體及點狀神經末梢和野生型小鼠相比無顯著差異。四週NRG1變異小鼠parvalbumin (PV)纖維密度較野生型上升33％，八週NRG1變異小鼠較野生型上升41％。NRG1深染細胞數，四週NRG1變異小鼠較野生型下降78％；八週NRG1變異小鼠較野生型下降97％。NRG1淡染細胞數，四週NRG1變異小鼠較野生型下降24％；八週NRG1變異小鼠較野生型下降43％。NRG1總細胞數，四週NRG1變異小鼠較野生型下降32％；八週NRG1變異小鼠較野生型下降約69％。四週NRG1變異小鼠ErbB4視密度較野生型上升約27％，八週NRG1變異小鼠較野生型上升約16％。 (ii)扣帶皮質1的L5： TH纖維密度，GAD67細胞體數及點狀神經末梢密度，PV細胞體數及纖維密度，NRG1深染細胞數，NRG1總細胞數和ErbB4視密度表現的改變和扣帶皮質1的L2/3類似。但NRG1淡染細胞數，四週NRG1變異小鼠較野生型無顯著差異，八週NRG1變異小鼠較野生型上升111％。 (iii)扣帶皮質II的L2/3： 八週NRG1變異小鼠tyrosine hydroxylase (TH)纖維密度較野生型上升103％，四週NRG1變異小鼠和野生型小鼠相較無顯著差異。四週NRG1變異小鼠GAD67細胞體數較野生型上升約30％，八週NRG1變異小鼠和野生型小鼠相較無顯著差異。四週和八週NRG1變異小鼠GAD67點狀神經末梢和野生型小鼠相比無顯著差異。四週NRG1變異小鼠PV細胞體較野生型上升約127％，八週NRG1變異小鼠和野生型小鼠相較無顯著差異。四週NRG1變異小鼠PV神經纖維密度和野生型小鼠相比上升約39％，八週NRG1變異小鼠較野生型上升61％。NRG1深染細胞數，四週NRG1變異小鼠較野生型下降98％；八週NRG1變異小鼠較野生型下降93％。NRG1淡染細胞數，四週NRG1變異小鼠較野生型小鼠上升約45％，八週NRG1變異小鼠較野生型無顯著差異。NRG1總細胞數，四週NRG1變異小鼠較野生型下降37％，八週NRG1變異小鼠和野生型小鼠相較無顯著差異。四週NRG1變異小鼠ErbB4視密度較野生型上升約14％，八週NRG1變異小鼠較野生型上升約18％。 (iv)扣帶皮質II的L5： TH纖維密度，GAD67細胞體數及點狀神經末梢密度，PV細胞體數及纖維密度，NRG1深染細胞數和ErbB4視密度表現的改變和扣帶皮質1的L2/3類似。但四週NRG1變異小鼠NRG1淡染細胞體數較野生型上升約37％，八週NRG1變異小鼠較野生型上升約78％。四週NRG1變異小鼠NRG1總細胞體數較野生型下降約31％，八週NRG1變異小鼠較野生型下降約29％。 3.體感覺皮質 (i) 體感覺皮質的L2/3：四週NRG1變異小鼠GAD67細胞體數較野生型小鼠上升約60％，八週NRG1變異小鼠較野生型上升32％。四週NRG1變異小鼠DCX7細胞體數較野生型小鼠上升約50％，八週NRG1變異小鼠較野生型上升100％。 (ii) 體感覺皮質的L4：四週和八週NRG1變異小鼠GAD67及DCX細胞體數和野生型小鼠相比無顯著差異。 (iii) 體感覺皮質的L5：四週NRG1變異小鼠GAD67細胞體數較野生型小鼠上升約44％，八週NRG1變異小鼠較野生型上升18％。四週NRG1變異小鼠DCX7細胞體數較野生型小鼠上升約128％，八週NRG1變異小鼠較野生型上升56％。 另外，定性發現，四週和八週NRG1變異小鼠PV細胞體數，NRG1淡染細胞數及ErbB4視密度在L2/3，L4及L5較野生型小鼠增加，NRG1深染細胞數及NRG1總細胞數較野生型小鼠減少。 4.側腦室： 四週NRG1變異小鼠DCX表現面積較野生型小鼠上升約46％，四週NRG1變異小鼠和野生型小鼠相較無顯著差異。：四週NRG1變異小鼠DCX表現面積和側腦室比例較野生型小鼠上升約34％，八週NRG1變異小鼠和野生型小鼠相較無顯著差異。 綜合以上所述，NRG1變異可能會影響胼胝體、扣帶皮質、體感覺皮質及側腦室這些核區，這可能為NRG1變異小鼠行為異常的原因之一。些異常行為背後的腦神經化學型態或許可以作為未來發展治療精神分裂症方式的基礎。

Neuregulin1 (NRG1) is growth and differentiation factor with a wide range of function in nervous system.NRG1 regulates development and migration of neurons. Recent molecular genetics studies implicate NRG1 is a promising candidate gene for schizophrenia. Mutant mice heterozygous for NRG1 show behavioral phenotype that overlaps with mouse models for schizophrenia. Studies of NRG1 mutant mice have provided support for the potential role of mutations in the gene as risk factor for schizophrenia. Schizophrenia is a devastating disease that affects the general population. The hypothesis that this disease is a developmental and neurotransmitter disorder of the nervous system. In previous studies, schizophrenia patients exhibit markedly reduced levels of GAD67 mRNA and dopamine in the dorsolateral prefrontal cortex. Thus, this study investigate the roles of frontal lobe in the mutation of nrg1 gene, by nissl stain and examining the expression of GAD67, dopamine, PV and DCX in 4 weeks and 8 weeks WT and NRG1 mutant mice (△TM+/-). Our results reveled that: (1) Corpus callosum(CC): There is no significant alternation in width and length of CC in 4wk and 8wk NRG1 mutant mice, but 4wks NRG1 mutant mice exhibit decreased area of CC. (2) Cingulate cortex (Cin): I. L2/3 and L5 of Cin1: The density of TH is increased in 8wk NRG1 mutant mice. There are no significant alternation in the number of GABAergic and PV neurons in 4wk and 8wk NRG1 mutant mice . There is no significant alternation in the expression of GAD67 but the density of PV is increased in 4wk and 8wk NRG1 mutant mice. II. L2/3 and L5 of Cin2: The density of TH is increased in 8wk NRG1 mutant mice. There is an increased in the numbers of GABAergic and PV neurons in 4wk mutant mice, but no significant alternation in 8wk NRG1 mutant mice. There is no significant alternation in the expression of GAD67 but the density of PV is increased in 4wk and 8wk NRG1 mutant mice. (3) L2/3, L4 and L5 of Somatosensory cortex (SSC): There is an increased in the numbers of GABAergic and DCX neurons in the L2/3 and L5 of SSC in 4wk and 8wk NRG1 mutant mice, but there is no significant alternation in the L4. (4) Lateral ventricle (LV): There is an increased in the area and ratio of DCX in 4wk NRG1 mutant mice, but there is no significant alternation in 8wk NRG1 mutant mice. It is known that the activity of NRG1 could disturb the expression of dopamine, GABA, and PV in cingulate cortex and somatosensory cortex. The mutation of NRG1 also affects the areas of corpus callosum and the expression of DCX in lateral ventricle Our results suggest that the activity of NRG1 is associated with the dopamine and GABA system in frontal brain region, leading to functional and behavioral changes, and may implicate mechanism of abnormality of NRG1 mutant mice.