72 What is Autism?
individuals suffer from this genetic defect. TSc2 (also known as hamartin) and
TSC2 (also known as tuberin) form the tuberous sclerosis protein complex that
acts as an inhibitor of the mechanistic target of rapamycin (mTOR) signaling
pathway, which in turn plays a pivotal part in regulating cell growth, prolifera-
tion, autophagy and protein and lipid synthesis. Remarkable progress in basic
and translational research has been made; some of its symptoms may be ame-
liorated through treatment, but tuberous sclerosis has no known cure. It is
caused by a genetic disorder, and is linked to many mental and physical prob-
lems, including epilepsy and intellectual disability. As with Fragile X syndrome,
we agree that tuberous sclerosis is an inherited genetic problem that should
not be a part of the ASD spectrum [59–61].
We maintain that some of the leading genetic diseases that greatly increase
the probability of developing autism are the result of chromosomal abnormali-
ties (e.g., Down, Angelman, Fragile X, Rett, and Cohen syndromes), and as
such should not be included in ASD because they are obviously genetic dis-
eases, not diseases caused by epigenetic factors, environmental factors and
other factors not primarily due to genetic causes. The inclusions of well‐estab-
lished genetic diseases have greatly hindered the investigations that are
attempting to find the real causes of ASD [62–64].
In the Table 2.1 we list other genetic diseases that are purely genetic disor-
ders and are not really neurodevelopmental conditions arising from environ-
mental factors. These impede finding the true causes of ASD and prevention
efforts.Is Finding Mutation the Path to Discovering the Origin of ASD?
Since the beginning of contemporary science, scientists have utilized mouse
models, and numerous other small animal models, to produce various theories
on autism. However, it should be noted that a Homo sapiens brain is both
extremely complex and large. It has over 100 billion neurons and 0.15 quadril-
lion synapses. If one is looking for genetic mutations and comparing this with
a mouse animal model, then one has to realize that these comparisons are not
accurate. For example, an average adult human weighs 62 kg, contains 3.7 tril-
lion cells (3.7×10^13 cells), and lives to be about 70 years of age. On the other
hand, an average mouse weighs about 20 g, or about 1/3,100 of an adult human,
therefore on a proportional basis it would contain roughly 1.2×10^10 cells, and
live for 3 years. The human genome contains approximately 3 billion of these
base pairs, which reside in the 23 pairs of chromosomes within the nucleus of
all our cells. Each chromosome contains hundreds to thousands of genes,
which carry the instructions for making proteins. The mouse genome is