Key Human Developmental Genes and Their Functions

Hox Genes (Homeobox Genes)

• -family of transcription factors
  -determining the body plan of an embryo along the cranio-caudal axis.
  -Specify the identity of different body segments, ensuring that structures like limbs and organs develop at the right locations.

Hox Genes (Homeobox Genes)

-control the development of the vertebral column, limb formation in humans
-controls the arrangement of nerves and muscles humans.

Pax Genes

• involved in organ development and tissue differentiation.

• regulate the formation of structures like the eyes, ears, and nervous system.

Pax6

is a critical gene for eye development. Mutations can lead to conditions like aniridia (absence of the iris of the eye)

Sonic Hedgehog (SHH)

• a signaling molecule that guides the development of various structures, like the brain, spinal cord, and limbs.
• plays a central role in patterning the neural tube and establishing the midline of the body.

Sonic Hedgehog (SHH)

-crucial for the development of the forebrain and the separation of the eyes.
-Mutations can lead to holoprosencephaly (forebrain fails to properly divide into two hemispheres)

Notch Signaling Pathway

-involved in cell fate determination, influencing whether a cell becomes a neuron, muscle cell, or another type of cell.

• plays a role in processes like neurogenesis, somitogenesis (formation of somites, which give rise to muscles and vertebrae), and angiogenesis (formation of blood vessels).

Notch Signaling Pathway

-is essential for the formation of the cardiovascular system and the development of the nervous system.
-Disruption of this pathway can lead to congenital heart defects and other developmental disorders.

Wnt Signaling Pathway

• involved in cell proliferation, migration, and polarity during development.
• plays a significant role in the formation of tissues and organs, including the nervous system, bones, and kidneys.

Wnt Signaling Pathway

-is critical for limb development and the formation of the dorsal-ventral axis (back- to-belly orientation).
-Abnormalities in this can result in conditions like cancer and congenital malformations.

T-box Genes (Tbx Genes)

• transcription factors that regulate the development of the heart, limbs, and other tissues.
  - involved in mesodermal differentiation (the formation of muscles, bones, and the circulatory system).

Tbx5

is essential for the development of the heart and upper limbs. Mutations can lead to Holt- Oram syndrome.

Fibroblast Growth Factors (FGFs)

• a family of growth factors that regulate cell proliferation, differentiation, and migration.
• involved in the development of the limbs, brain, and organs like the lungs and kidneys.

FGF8

-is important for limb and brain development.
-Disruption of this signaling can result in skeletal abnormalities and impaired brain development.

Transforming Growth Factor-Beta (TGF-β)

• a signaling molecule that regulates cell growth, differentiation, and apoptosis.
• plays a role in the development of the heart, lungs, and blood vessels.

Transforming Growth Factor-Beta (TGF-β)

-is essential for heart valve formation and the development of the immune system.
-Abnormal signaling can lead to fibrosis (excessive tissue growth) and congenital heart defects.

BMP (Bone Morphogenetic Protein)

• a group of growth factors that are part of the TGF-β superfamily.
• play a key role in bone and cartilage development, as well as the formation of the nervous system and kidneys.

BMP4

-is involved in the development of the dorsal- ventral axis and limb patterning.
-Mutations can lead to skeletal disorders and congenital abnormalities.

Retinoic Acid Signaling

• derived from vitamin A, acts as a signaling molecule that regulates gene expression during development.
• involved in the formation of the limbs, heart, eyes, and central nervous system.

Retinoic Acid Signaling

-is essential for the development of the anterior- posterior axis and the proper segmentation of the hindbrain.
-Excess or deficiency of this during pregnancy can cause birth defects.

Nodal Signaling

• is a signaling protein that belongs to the TGF-β family and is crucial for establishing left-right asymmetry in the body.
  -It is also involved in mesoderm formation and the development of the heart and gut.

Nodal Signaling

-ensures that organs like the heart and stomach are positioned correctly in the body.
-Disruption can lead to situs inversus.

Holt-Oram syndrome

caused by Tbx abnormalities, affects the heart and arms.

situs inversus

-caused by nodal signaling disruption
-where the organs are mirrored from their normal positions.