assessing motor function in the thyroid hormone-related mouse model using the ladder beam test

<meta charset="utf8"></head><body>Merdiven Işın Testi Kullanılarak TH ile İlgili Murin Modellerinde Motor Performansın Değerlendirilmesi

Thyroid hormone (TH) is indispensable for brain development1. In particular, its role in the cerebellum is critical because TH deficiency in early life causes aberrant cerebellar development1,2. For example in congenital hypothyroidism, patients display a series of neurological retardation including cognitive and motor deficits3. To unveil the role of TH in cerebellar functional development, some studies have limited TH deficiency in a cerebellar cell-specific manner4. However, compared to generalized congenital hypothyroid mice, in which all tissues and cells are affected by TH deficiency, such cerebellar-specific models display so subtle ataxia that the conventional behavior tests, such as rotarod, footprint, and balance beam tests, barely detect the differences. Thus, to fully investigate the TH effects on cerebellar function, a new assessment tool is needed to detect a subtle change in the motor coordination of model mice.
The rotarod test is the most common tool for assessing motor coordination, originally developed by Dunham and Miya5 and later applied to an accelerating version by Jones and Roberts6. The latency to fall from the rotating rod is interpreted as the test for motor coordination, and its simplicity and conciseness make it commonly used among behavioral researchers studying motor function7. However, the ease of use of this test is a double-edged sword. Because the rod automatically rotates, mice can cling to and stay on the rotating rod without moving. Furthermore, mice may intend to fall off rather than keep balancing on the rotating rod. In either situation, the validity and reliability of the test are questionable for assessing &#34;pure motor coordination&#34;7. In other words, it does not accurately target the cerebellar function and involves other factors such as muscle strength for gripping.
Instead of the conventional tools for motor coordination assessment, here we present a novel behavior test called the &#34;ladder beam test,&#34; which is recently developed in our laboratory. The horizontal ladder walking test was designed to assess cerebellum-related complex motor abilities: feed-forward prediction and integration of motion8. The test device was composed of four pieces of plexiglass with holes (Figure 1). The four plates were connected in parallel by screws and sticks inserted into the holes on the plates. Two outer plates were used to stabilize the device and two inner plates were used to design the various kinds of ladder rungs (Figure 2C). The width of the rung was adjusted depending on the animal size to minimize the animals&#39; moving backward (Figure 2B). The distance from the start point to the goal was 110 cm. The device was located 60 cm above the bench and a safety cushion was set under the device (Figure 2A). The dark chamber was put near the goal to motivate the animals to move toward the goal (Figure 2A).
We examined the TH effects on cerebellar functional development by using transgenic mice expressing dominant-negative TH receptor (TR) in cerebellar Purkinje cells (Mf-1/FVB mice). In both rotarod and ladder beam tests, we observed cerebellar ataxic phenotype in Mf-1/FVB mice; however, the ladder beam test succeeded in detecting more significant differences than the the rotarod test (Figure 3). In addition, motor learning ability can be more thoroughly assessed in ladder beam test (Figure 3B,C). As a cellular background of such a behavioral phenotype, the induction of long-term depression (LTD) was inhibited and instead, long-term potentiation (LTP) was induced following an LTD-inductive stimulation in Mf-1/FVB Purkinje cells9. LTD is essential for motor coordination and motor learning in the cerebellum10. Many studies have reported motor deficits and inhibition of LTD in knockout or mutated mice for key regulator genes in cerebellar function, however, no studies have ever reported the induction of LTP following an LTD-inductive stimulation11,12. Taken together, this phenomenon may be unique to Mf-1/FVB mice or TH-deficient mice (the same phenomenon was observed in adult-onset hypothyroid mice), suggesting that TH regulates cerebellar function differently from the other key proteins. If so, it is plausible that mice with abnormal TH action do not display cerebellar ataxia in the same way as other model mice. This again emphasizes the need for a specific method for assessing TH effects on cerebellar function. This paper presents a novel protocol to investigate TH effects on cerebellar function using the newly-built ladder beam test.

<meta charset="utf8"></head><body>Yazar Spotlight: Farede Tiroid Hormonu Kaynaklı Motor Değişikliklerinin Doğru Bir Şekilde Değerlendirilmesi

Tiroid hormonunun serebellar fonksiyon üzerindeki etkilerini araştırmak için çok yönlü, davranışsal bir yöntem

To comprehensively understand the various facet of thyroid hormone involvement in the central nervous system, we investigated spectrum of perspectives, spanning the hair phenotype to molecular adulation at the single-cell level. We are also looking on connecting those different dimension of the vibration to elucidate the mechanism of thyroid hormone in brain development. The mainstream research in the field primarily centers around the molecular biology with numerous researches investigating the impact of thyroid hormone on gene expression.Nowadays, the increasing focus on behavior analysis to uncover the role of thyroid hormones, particularly within the central nervous system. This approach could explain the specific behaviors observed in certain thyroid hormone-related diseases. With the current level of available techniques, such as the rotarod test, researchers often struggle does this behavioral patterns, especially motor performance, in motor mice.This hinders the translation of reside to clinical situations. Our protocol has been designed to assess several motor alteration in mice, facilitating a clear interpretation of behavior observations.

Merdiven Işını Testi Kullanılarak Tiroid Hormonu ile İlişkili Fare Modelinde Motor Fonksiyonun Değerlendirilmesi

assessing-motor-function-thyroid-hormone-related-mouse-model-using

Research

JoVE Journal

Behavior

Assessing Motor Function in the Thyroid Hormone-Related Mouse Model Using the Ladder Beam Test

24 Views. Before subjecting the mouse to the ladder beam test, perform an initial habituation training on the completely assembled ladder beam test apparatus. To do so, place the mouse at the edge of the ladder designated as the starting point. Using an air puff, encourage the mouse to move forward on the ladder rung towards the goal.Repeat the training until the mouse gets habituated to walk on the ladder rungs. To perform the motor performance test, place the already habituated mouse at the st...